Genetics exam 2

Fearon-Vogelstein Adenoma-Carcinoma Model

Mutation of APC --- Mutation of K-ras

remove covalent chemical marks in DNA or histones

"Erasers"---

(CML)-- t(9;22) c-Abl+Bcr kinase +GAP are spliced to form' constitutively active chimeric kinase that drives cell proliferation

Philadelphia chromosome

a gene that alters phenotype in a non-allelic gene only a few modifier genes have been recognized for their effect so far

Modifier: Genetic Modifiers

of sex chromosomes, fetus survives = 45, X Turner Syndrome

Monosomy

Familial Aggregation Ex:family relatedness percent

Monzygotic twins -100% common alleles First degree relatives: Sib-sib ---50% parent-child—50% (child has one out of 2 possible alleles) dizygotic twins—50%

Individual or tissue with two or more somatic chromosome numbers but derived from the same zygote. Non-disjunction in early embryo and both cell lines persist. Accounts for 1-2% of Down's Cases Can also occur in germline of gonadal tissue rare occurrence of child not matching the mother's assumed DNA contribution

Mosaicism

trait is either present of absent ex: patient with rheumatoid arthritis (or not)

Qualitative Trait: Polygenic Inheritance

two types of single gene defects are Nuclear and Mitochondrial. Most conceptions with single gene defects result in live births.

Single gene defects (Mendelian genetics)

-originate in epithelial tissue (Ex: cells lining the intestinal, lung bronchi or mammary duct epithelium

] Carcinoma

Mode of RP inheritance:

autosomal dominant 15-25% cases autosomal recessive 5-20% cases X-linked 5-15% cases Unknown 40-50% cases Digenic rare (mutations in both ROM and PRPH2 genes) Genes where mutations involving RP have been found: Rhodopsin (RHO:20-30%); U4/U6 small nuclear riboprotein (PRPF31:5-10%); peripherin-2 (PRPH2: 5-10%)

a trait/gene that is located on an autosome=

autosomal inheritance

—gain or loss of one or more chromosomes

chromosomal aneuploidy

--accumulation of extra set(s) of chromosomes

chromosomal polyploidy-

if only one twin has disease they are "______" if only one MZ twin has type 1 diabetes—argues for its complex inheritance and environmental contribution 1. exposure to infection 2. diet 3. epigenetic gene expression changes

discordant

Genome Sequence Complexity protein coding

dispersed gene families (actin=5-30 copies), keratin (20+ copies), histones (100-1000 copies)

Mutated c-onc have a _____ effect!

dominant

only one copy of gene/pair of chromosomes needed to produce the phenotype example: possible alleles HH, Hh, hh -Hh is affected and hh is lethal HH is wildtype

dominant expression--

dup

duplication 46, XY, dup (13q14)

Size of genes varies: some with single exon to

dystrophin with 79 exons (2.5 Mb)

HATs

histone acetylases

Synaptonemal complex

holds chromosome homologues in close proximity so that crossovers can happen

Incomplete Dominants examples -skeletal disorder short stature dwarfism -premature coronary disease

homozygout dominatn= lethal Achondroplasia Familial Hypercholesterolemia

Heteroplasmy vs homoplasmy

if mother has a mixture of normal and mutant mitochondria, oocytes can have variable disease phenotypes based on number of affected mitochondria

Histone Acetylation (HAT enzymes) turns on/off genes Deacetylation (HDAC) genes turn on/off genes

on off

Activation of ___ or anti-apoptotic genes is dominant and requires only a single mutant allele. Mutations in tumor-suppressor genes are recessive; when both alleles are mutated or inactivated, cell growth is unregulated or genomic integrity is compromised.

oncogenes

Complex that allows for homologous chromosomes to cross over forms during

synaptomeal complex meiosis phase 1

Genome Sequence Complexity non-coding

tRNA genes (50 sites with 10-1000 copies/site) telomere

centromeres divide

longitudinally

micro rna repression

of mrna

methylaiton acts to turn on/off genes

off

Edward's Syndrome

-trisomy 18 viable

-end product 1N gametes

Meiosis

Smallpox, cowpox Suspected -unknown

Pox viridea

Consanguinity

first cousin or direct family member

Hallmark of tumor cells is

genetic instability:

ish

in situ hybridization

ter

terminal end pter or qter

(v-onc)

viral-oncogenes

=mutant cells restricted to gametes Ex: parents who are phenotypically normal but have an affected child with disease after analysis for an autosomal dominant or X-linked disease is ruled out carrier status for mutation must be ruled out then pedigree can be explained by germline mosaicism 6% of severe lethal forms of osteogenesis imperfecta are germline-type I collagen also some cases of Hemophila A, Hemophilia B, and DMD (up to 15% of mothers) may result from germline mosaicism in a parent

"Pure" germline mosaic

mutant cells not present in gametes manifests as a segmental or patchy abnormality depends on when mutation occurred and what cell lineage it occurred in Ex: Segmental Neurofibromatous 1 (NF1)—mosaicism resulting after conception patient has normal parents, but patient has children who are affected if they have typical NF1 phenotype (mutation in gametes that pass it on).

"Pure" somatic mosaic=

effector proteins bind to specific epigenetics marks to "interpret" marks

"Readers"---

add covalent chemical marks to DNA or histones

"Writers"---

up-regulation of angiogenesis and down-regulation of of anti-angiogenic factors significant transformation that leads to more lethal tumors

"angiogenic switch"

lambda r Relative Risk Ratio

(Prevalence of the disease in the relatives of the affected family member )/(Prevalence of the disease in general population) the larger the λr value=greater the familial aggregation a λr=1 , family has no aggregation=family prevalence equal to population incidence

what might happen to heterochromatin regions

-

Apoptotic program has three phases:

-- initiation phase----activation of pathways from external signals (death receptor ligands) decision/effector phase—disruption of mitochondrial membrane potential and integrity --releaase of cytochrome c into cytoplasm that activate proteases/nucleases -- degradation/execution phase---cell loss Disruption of mitochondrial function is central to loss of cell viability

Genome instability is a universal characteristic of cancer cells

---defects in chromosome segregation ---DNA repair deficiencies the weakened capacity to maintain genome integrity generates more DNA/chromatin changes invasive cancer cell development p53 mutated cells ---can show chromothripsis; shattering chromosomes into many fragments followed by end-joining repair

Metastasis is a multistep process:

---detachment of tumor cells from primary tumor ---penetration through basement membrane by degrading the extracellular matrix (ECM) ---transport to foreign tissue sites-> blood and lymph >tumor from different tissues have characteristic invasion patterns (transport type) > must evade host defense mechanisms (immune surveillance) > extravasation (from blood or lymph thru vessel wall) to gain residence in new spot ---acquisition of growth stability in distant tissue sites

Crossover can occur in meiosis

1

List of Phenotypes that define tumor cells:

1) Immortality 2) Decreased dependence on growth factors for proliferation 3) Loss of anchorage dependent growth /altered cell adhesion 4) Loss of cell cycle control 5) Reduced sensitivity to apoptosis 6) increased genetic instability 7) Angiogenesis

In contrast to RSV, many retroviruses have lost part of their genome to accommodate an oncogene (see fig). This has two consequences:

1) The protein encoded by the oncogene becomes part of a fusion protein with other virally-encoded peptides attached 2) Virus cannot make all of itself. To replicate and bud from the host cell needs products of another virus (helper virus).

Two hypothesis NON-DISJUNCTION:

1) problem with spindle formation in aging female 2) recombination failure in some of the females fetal primary oocytes

Five phases for mitosis-entire process usually lasts 1-2 hours

1) prometaphase (prophase) 2) metaphase 3) anaphase 4) telophase 5) cytokinesis

Must overcome two critical obstacles to be cancerous

1) replication of telomeres (linear 5'ends of DNA---other wise chromosomes not protected from shortening in tumor tissue and normal tissue from same patient telomerase activity is increased above normal in tumor tissue 2) loss of growth control via loss of tumor suppressor activity find inactivating mutations for p53 and Rb in tumor cells

Sometimes difficult to measure and correctly interpret λr values Potential Sources of Bias:

1. Ascertainment Bias: a) families with more than one affected individual more likely to come to researchers attention/clinic -proband gives family history (recall bias) b) one twin recruits the other (volunteer-based ascertainment) 2. Heritability Interpretation a) different population (American Indian vs. African sub-continent) may give different heritability estimates 3. Potential Genetic Drift or Epigenetic Differences a) genotype can arise by somatic rearrangements/rare somatic mutations b) in females, mosaicism from X-inactivation 4. Environmental exposures for twins—even in utero may be different

Chromatin structure changes mostly arise by chemical modification of either 1. DNA strands 2. Histones in nucleosome

1. DNA strands addition of methyl cytosines; removal methyl cytosines (note: mCp behave as C so still base pair with G). Highly methylated DNA is characteristic of heterochromatin and low level methylation is associated with accessible genomic sites) 2. Histones in nucleosome different types of post-translational modification at specific amino acid positions histone acetylation histone deacetylation (open chromatin) (condensed chromatin)

Seven classes of oncogenes---defined by cell location and cellular activity

1. growth factors 2. growth factor receptors 3. membrane associated guanine nucleotide-binding proteins (G proteins) 4. serine-threonine protein kinases 5. cytoplasmic tyrosine kinases 6. nuclear proteins 7. cytoplasmic proteins engaged in cell survival

Tumor cells from any organ can frequently grow in suspension or soft agar (one test for cancer cell phenotype)

1. Loss of anchorage dependent growth is significant > parent cell's ability to leave primary tumor site and invade elsewherein the body (metastasis) > represents a resilient tumor state---makes tumor difficult to treat > process of conversion from benign to life-threatening cancer 2. Acquisition of loss of anchorage dependence requires new characteristics---ability to proteolytically cleave basement membrane barrier and to colonize and grow in another tissue

Readers may recruit additional proteins to create different chromatin states such as:

1. compaction 2. changes in nucleosome spacing/structure (chromatin remodeling) (opening access to transcription factors) 3. histone substitution (non-standard histones) -recruitment of regulatory factors

Two sources of genetic change that can produce disease:

1. mutations in DNA (doesn't necessarily change the epigenome) 2. uniparental disomy (both chromosomes come from same parent) a. Epigenetic marks the same if from same parent

Symptoms of mitochondrial disease may include:

1. poor growth 2. muscle weakness and loss of coordination 3. visual problems 4. hearing problems 5. learning disabilities, 6. heart disease, liver disease, kidney disease, 7. gastrointestinal disorders 8. respiratory disorders 9. neurological problems (seizures; neurodevelopmental disorders) 10. autonomic dysfunction 11. dementia 12. diabetes mellitus

--"Dolly" experiment: showed that transplanting a differentiated nucleus into oocyte cytoplasm allowed the zygote to develop to adult animal---epigenome marks had to be reset to allow that to happen

1. somatic nuclear transfer

Epigenome in differentiated cells is reprogrammable:

1. somatic nuclear transfer--"Dolly" experiment: showed that transplanting a differentiated nucleus into oocyte cytoplasm allowed the zygote to develop to adult animal---epigenome marks had to be reset to allow that to happen 2. Induced pluripotent stem cells (iPSC) demonstration that it takes only 4 transcription factors to initiate reprogramming from a differentiated fibroblast to an stem (embryonic)cell ---epigenome marks had to be reset to allow that to happen

Incidence of reciprocal translocation in general population is

1/500

Mitochondrial genome encodes ____ proteins that function in the respiratory complexes Nuclear genome encodes ___ proteins with mitochondrial function

13 1500

Homeobox genes are located on Chr

2, 7, 12 and 17

Outcomes of Meiosis:

1: division of chromosomes so that a child receives a maternal and a paternal set no set will be identical: 1/223 probability 2: Crossing over generates diversity=gene shuffling some chromosomes have alternating genomic regions from each parent n= number chromosomes c=[DNA] Note: gametes=haploid (1N) content of DNA

Cancer cells can evade apoptosis by two means

1st: Bcl-2 is overexpressed ---apoptosis is suppressed Bcl-2 oncogene ---identified as a chromosomal translocation breakpoint that occurred in B-cell derived tumors (translocation activates Bcl-2 driven by IgH promoter) Result: cells survive that ordinarily would die 2nd: suppression of the Fas receptor-- mutations in ligand binding domain or intracellular domain or newly described synthesis of "decoy" receptors in cancer cells - Result: bind but don't induce apoptosis

demonstration that it takes only 4 transcription factors to initiate reprogramming from a differentiated fibroblast to an stem (embryonic)cell ---epigenome marks had to be reset to allow that to happen

2. Induced pluripotent stem cells (iPSC)

Translocations: Quadrivalent

2:2 segregation Segregation of the quadrivalent during the later stages of meiosis I can occur in several different ways. If alternate chromosomes segregate to each gamete, the gamete will carry a normal or balanced haploid complement With fertilization, the embryo will either have normal chromosomes or carry balanced arrangement.

Cancer is the ___ (ranking) leading cause of death in the United States Cancer in some form is estimated to strike approximately 30% of the population accounts for about 20% of annual deaths accounts for 10% of medical care costs (in developed countries)

2nd

Turner Syndrome

45, XO female Monosomy

More than ___% of Mendelian Disorders are autosomal dominants Incidence can be high:

50 1/500 for familial hypercholesterolemia in European or Japanese decent 1/550 myotonic dystrophy in Charlvoix and Saguenay-Lac Saint Jean regions of Quebec 1/2500-3000 for Huntingdon's in population of Northern European descent (also neurofibromatosis, and polycystic kidney disease)

At meiosis carriers of a balanced insertion-deletion are at __% risk of producing unbalanced haploid gametes. Random assortment of chromosomes results in____% inheriting either the deletion chromosome or the insertion chromosome BUT NOT BOTH.

50 50

induces an intracellular cascade of kinase that support cell proliferation

: ras

Process of tumor formation driven by accumulation of mutations in key genes that encode functions for cell cycle regulation, cell growth and programmed cell death. ---each successive mutation confers those cells with a growth advantage ---allows cell clones to out grow "normal" neighbors

=> Clonal Evolution

In appropriate gene silencing: -altered heterochromatin distribution can silence active genes -chromosome translocation or inversion can bring an active gene into heterochromatin region

=POSITION EFFECT

If parents are related , chances of a mutant allele at the same locus increase because, They both could have inherited the same allele from a single common ancestor ________ (relatives are closer than second cousins) Risk of complications for offspring from a consanguinous marriage rise to 3-5% about double than that for an non-consanguinous marriage Incidence for cousin marriages in the USA is low but it does remain common for some ethnic areas where 20-60% of marriages may be between cousins Xeroderma Pigmentosum: Defective DNA repair common in first cousin marriages

=consanguinity

Chromosome Karyotype Dark bands

=heterochromatin "inactive"

Consanguinity is measured by the coefficient of inbreeding (F)—the probability that the homozygous mutant alleles have been inherited from the same ancestral source

=identity by descent

Types of Dysregulation:

> normal expressed genes become "heterochromatinized" > reduction of gene silencing and previously silent genes become active

polyploidy Frequently see in cells grown from material from spontaneous miscarriages Causes:

> retention of a polar body in oocyte division > formation of a diploid sperm > fertilization of an oocyte by two sperm (dispermy)

Co-Dominance - ABO Blood Groups Blood Type is controlled by three alleles - A, B, and O Alleles _____ co-dominant—both expressed ____a recessive allele

A & B O

Translocation: Robertsonian products

A carrier of a balanced reciprocal translocation can produce unbalanced gametes. When fertilized, some of the resulting zygotes will have partial trisomy and partial monosomy in defined chromosomal regions.

Chromosome Nomenclature

A given point (or gene location) identified by: chromosome number: 1-22 chromosome arm: p or q Chromosome band: 1-X CFTR: 7q31.2 Gaucher GBA:1q21

Cytogenetic: preparation metaphase chromosomes steps WE SHOULD KNOW

A peripheral blood sample is taken to isolate WBC WBC cultured in medium containing PHA (a mitogen) to stimulate cell division and growth colchicine added to culture—drug that prevents mitotic spindle formation cell division is arrested during metaphase when chromosomes are maximally visible cells put in a hypotonic solution cells swell and dropped on a slide lyse on a slide - and metaphase chr are captured

Kinetochore

A specialized region on the centromere that links each sister chromatid to the mitotic spindle.

LU repeats—33with sequence similarity to a signal recognition particle from protein synthesis---cut by Alu I restriction enzyme --(act as transposons- move spontaneously about genome)

ALU repeats—300

Numerical abnormalities of independent chromosomes(deviation from normal 46, XY) are called

ANEUPLOIDY

Colds, acute respiratory disease Adenocarcinomas (glandular epithelial tissues)

Adenovirus

Many loci have more than one mutant form: CFTR has 1400 documented mutations Gaucher disease has over 1000 mutations

Allelic Heterogeneity

Gaucher: GBA gene

Allelic Heterogeneity N370S mutant-Type 1 disease L444P mutant—Type 2 disease

Diagnosed postmortem neuropathology findings of characteristic protein aggregates (β-amyloid plaques and neurofibrillary tangles no obvious Mendelian inheritance pattern; does show familial aggregation MZ twin studies -concordance 50% Alleles consistently associated with late onset Apolipoprotein E (APOE) -APOE has three alleles ε2, ε3, ε4 (substitution of Arg for cysteine) 2-3 fold more risk in individual has at least one APOE-ε4 variant increased risk if homozygous ε4/ε4 at earlier age---ε4 allele a predisposing factor increased risk with traumatic brain injury -boxers, football player, soldiers with blast injuries predisposing but does mean that you will get disease

Alzheimer's Disease

Genes on Chr. 21 -many within critical region for Down's Syndrome

Amyloid β-precursor 3 purine synthesis enzymes SOD-1 (superoxide dismutase) Crystallin αA DS critical region

occurs when one segment of a chromosome is inserted into another Chromosome ---if moved from another chromosome and ______ =balanced karyotype ---if lost from another chromosome and ___ then= unbalanced karyotype

An insertion

Centromeres divide and separate-drawn to opposite poles of cell

Anaphase:

maternally inherited genomic imprinting UPD example of

Angelman: heterogeneity

Tumors: ability to develop new blood vessels (sprouting of capillaries from existing vessels) to supply increased growing tissue the cancer would be restricted to a volume of a few mm3 dependent on O2 and other nutrients ability to diffuse across the tumor space if O2 can not diffuse--- center of mass becomes necrotic

Angiogensis

Disease examples: Huntingdon's disease (HD): neuropathic condition degeneration of cortex and striatum Patients present with characteristic: (autosomal dominant) motor abnormalities in mid-life, personality changes loss of cognition leading to death Passed to progeny -50% risk to each offspring (male meiosis susceptible=parental bias) Heterozygotes and homozygotes similar course of disease -homozygous more rapid decline Most HD patients show symptoms by age 40 but age of onset is variable As the disease is passed through the pedigree from generation to generation—disease Appears at earlier and earlier ages when transmitted by an affected male=> Anticipation CAG repeat (poly Q) in the coding region of huntingtin (no known function) normal: 9-35 repeats >39 expansions always produce disease Premutation : CAG repeats of 29-35 that are capable of expansion past 40 to cause disease

Anticipation or Parental Bias

Other differences: -length and base sequence of the repeated unit -the number of repeats in a normal, presymtomatic or affected individual -location of the repeated unit within the gene -pathogenesis of disease -degree to which instability occurs in mitosis or meiosis -parental bias where expansion occurs

Anticipation or Parental Bias

There are over a dozen known disease with this apparent mechanism -all of the conditions have neurological symptomology -mode of transmission is autosomal, recessive or X-linked

Anticipation or Parental Bias

Largest kindred of HD patients -Lake Maracaibo Venezuela -shows founder effect -descendants of a single individual with either mutation or premutation

Anticipation or Parental Bias Huntingdon's disease

genetically controlled cell death essential for tissue remodeling during embryogenesis maintenance of homeostatic balance of cells numbers in adults Loss of apoptotic balance may be the basis of many diseases including cancer and neurodegenerative diseases

Apoptosis:

Expressed in both homozygous (HH) and heterozygous individuals (Hh) with this genetic inheritance pattern

Autosomal Dominance

Chacacteristis of Phenotype appears in every generation with each affected individual having an affected parent (exceptions low penetrance; new mutation Any child of an affected parent has a 50% of disease Phenotypically normal family members do not transmit the disease phenotype to their children (exceptions low penetrance or variable expressivity) Males and females equally likely to transmit phenotype to children of either sex Isolated cases may be due to a new mutation; especially if fitness is low

Autosomal Dominant

: is seen when the chromosome carried are heterozygous for a locus (TK+/TK-) One normal (TK+) and one abnormal (TK-). It is often possible to trace inheritance through many generations of a family

Autosomal Dominant Trait

males and females are equally affected with this genetic inheritance pattern

Autosomal Inheritance

de novo mutation at same allele as carrier parent: Acquired mutation frequency 1/105-106 Unlikely since the de novo mutation rate is so low and carrier frequency is high BUT it can not be ruled out for some instances although more common in autosomal dominant

Autosomal Recessive by de novo mutation

Most commonly ______ disorders are more severe in homozygotes than heterozygotes (referred to as semi-dominant or incompletely dominant)

Autosomal dominant

tumor suppressor protein functions to maintain constitutive heterochromatin Mutations in ____ cause loss of heterochromatin organization Reduced centromeric heterochromatin mitotic recombination and genome instability

BRAC1 BRAC1

found in rare families/ obesity varied intellectual disability/ retinal degeneration polydactyl/ genitourinary malformations Mapped to mutations in 14 different genes -most cases are autosomal recessive -rare cases are found where homozygous for mutation in one gene and heterozygous for mutation in another of the 14 known genes

Bardet-Biedl Syndrome—

To prevent heterochromatin silencing some regions have evolved

Barrier elements (Insulators)—protect genes from surrounding environment Nucleosome free areas

-defect DNA helicase increase in somatic recombination and sister chromatid exchange

Bloom Syndrome

BRCA 1 ad BRCA 2 are cell cycle regulators (G1 check point) Block entry into S phase by inducing CDK1 inhibitor p21 Promote DNA repair by binding to RAD5 If mutant loss of cell cycle control—unregulated growth

Breast and Ovarian Cancers:

-t(8,14) c-myc proto-oncogene expressed from Ig promoter

Burkitt's lymphoma

should be considered a molecular genetic disease ---mutations in critical genes activation of proto-oncogenes, genetic profile of tumor tissue always has gene mutations (may not be the same gene mutations)

Cancer

Death Receptors and ligands

CD95---Fas cluster member Death receptors (DR) 3, 4, 5 (Death domain binding site) TNFR1-tumor necrosis factor receptor 1

Example _________ caucasian population 1/2000 children has the disease (virtually non-existent in Asian population and rare in African Americans) frequency of carriers: 1/29

CF: cystic fibrosis

: sometimes clinically indistinguishable disease from different mutation BUT: different mutants can produce a clinical spectrum of disease classic cystic fibrosis: severe progressive lung disease, pancreatic insufficiency and congenital absence of the male vas deferens Other CF patients ( carriers of different alleles) may have : > lung disease but normal pancreatic function > only abnormality of the male vas deferens

CFTR

Not a single disease ---name used to describe the rapid and uncontrolled cellular proliferation (neoplasia) that produces a mass/tumor (neoplasm)

Cancer

process that produces genetic mutations induced by chemicals or physical agents (initiation promotion progression localized tumor) initiation-irreversible change in single cell promotion-increased proliferative ability in initiated cell progression-acquisition of more genetic damage that allows cell(s) to proceed to malignant phenotype

Carcinogenesis:

maintain integrity of genome by repairing DNA BRAC1, BRAC2, MSH2, MLH-1, WT-1, NF-1

Caretakers:

individuals with disease (case) are compared to controls without disease (control) controls suitably chosen for environmental exposure, occupation, geographic area, and other parameters as appropriate (age, ethnicity) compare frequency of disease found in patient families (positive family history) to frequency of disease among matched controls Calculation of odds ratio: family history of MS 3.5% of first degree relatives also had MS case controls 0.2% of families had MS history thus, MS shows significant familial aggregation: 18X more likely for a first degree relative to have MS

Case-Control Studies for Familial Aggregation

Clinically: coloboma of the iris anal atresia with fistula, downslanting palpebral fissures, preauricular tags and/or pits, frequent occurrence of heart and renal malformations, normal or near-normal mental development.

Cat Eye Syndrome (Schmid-Fraccaro Syndrome) Results from an inv dup 22q11 Aneuploidy can involve partial chromosome increases or deletions

Two centrioles form with microtubules that move to opposite poles of cell Chromosome condensed with sister chromatids formed Nuclear membrane disintegrates Microtubles of mitotic spindle attach to chromosome centromeres

Cell Division-Mitosis

divides chromosomes into p and q arms

Centromere

chromatids join at central core—consists of repetitive DNA responsible for chromosome movement

Centromere region-

not single gene defects- do show genetic variation frequently show familial aggregation more common among close relatives of the proband may show lack of penetrance in family members because of crucial of non-genetic factors in disease

Characteristics of Complex Disease Inheritance

Characteristis of ______ Phenotype seen in sibship of the proband Males and females equally affected Both parents of an affected child are asymptomatic carriers of mutation Parents may be from consanguinous mating (especially if condition is rare in general population Recurrence risk is ¼ for sib of the proband

Characteristics: Autosomal Recessive

Presence in an individual of two or more distinct cell lines—different genetic origin Dispermic chimeras: result of double fertilization Sperm fertilize two ova and those ova fuse to one embryo Different sex embryos fused-true hermaphrodite (XX/XY) Blood chimeras-exchange of blood between twins in utero

Chimerism

Most do not result in live births. Although ~60% of spontaneous abortions have a normal karyotype, autosomal trisomies are found in ~20% of spontaneous abortions.

Chromosomal disorders: chromosomal disorders

--tumor cells typically have abnormal karyotypes ---missing chromosomes (deleted ) ---extra chromosomes (duplication and partial duplications) ---structural rearrangements (inversions, translocations)

Chromosomal instability (CIN)-

Consequences of errors in chromosome replication and division Many different types of abnormalities have been documented. Identified by classical methods—karyotypes and now by molecular methods where more specific identity of genes can be established

Chromosome Abnormalities

each chromosome composed two identical DNA strands called "sister chromatids" Sister chromatids joined at a primary constriction= centromere (repetitive DNA; movement during cell division) that divides a metacentric chromosome into two arms = "p" petite and "q" (grande) the end of each sister chromatid has a telomere-that seals the end and maintains integrity

Chromosome Morphology:

distinguish species and enable transmission of genetic information from one generation to the next vehicles that facilitate reproduction and maintenance of a species

Chromosome:

Superimposed on the cell cycle are many positive and negative regulatory intersection points one family of regulators is the cyclin dependent kinase inhibitors (CKIs) two families of CKIs---

Cip/Kip family and the INK4 family

all the proteins in this family ---broad specificity---bind and inactivate most of the cyclin/cdk complexes that are needed for the progression of the cell cycle p21 is stimulated by p53 when DNA damage detected---cell cyle stopped for DNA repair

Cip/Kip family members: p21/ Cip1/ waf1/Sdi1, p21/Kip1, p57/Kip2

Normal development for 6-18 months (girls very few males seen) MeCP2 protein loss---loss of recognition of methyl cytosine Functions in neuronal maturation In girls phenotype partially determined by X-inactivation pattern Affected girls regress rapidly in loss of language and motor skills Condition eventually stabilizes Stereotypical hand wringing movements Growth retardation, seizures, austic behaviors, microcephaly, mental retardation Note on males: Originally thought that no MeCp2 was lethal Post-zygotic mutation or specific missense mutations have been seen on males

Clinical: Rhett Syndrome

_______-phenotypic expression for two allele at locus (ex: ABO blood group)

Co-dominance

This technique reveals the loss or gain of chromosomal regions in test samples (for example, derived from a tumor) relative to normal controls.

Comparative Genomic Hybridization (CGH)

Some of the most frequent multifactorial disorders (not part of a syndrome)

Congenital Heart Malformations (CHDs)—incidence 4-8/1000 live births -cause usually unknown and believed to be multifactorial -exposure to teratogen /infection (rubella) 2. Cleft Lip± Cleft Palate incidence 0.4-1.7/1000 live briths 3. Neural tubes defects incidence 2-10/1000 live births (-spina bifida and anencephaly 4. Pyloric stenosis incidence 1/1000 live births (more common in females) 5. Neuropsychiatric diseases 4/100 in population worldwide 6. Coronary Artery Disease

Since most autosomal alleles are "hidden" in carriers it can be several generations before they appear in a family pedigree ---appearance requires a carrier x carrier mating

Consanguinity

while DNA sequence invariant, epigenome is cell-specific and can vary with cell state

Corollary:

90% of cases sporadic or de novo mutations Remainder caused by parental unequal crossing-over of a balanced translocation in a parent.

Cri du Chat Syndrome (del5p) or 5p monosomy

difficulty swallowing and sucking; low birth weight and poor growth severe cognitive, speech, and motor delays; behavioral problems such as hyperactivity, aggression, tantrums, repetitive movements; unusual facial features that change over time; Excessive drooling constipation; small head and jaw and wide eyes Newborns have a characteristic "cat like" cry due to under-developed layrnx

Cri du Chat Syndrome (del5p) or 5p monosomy

Modifier Genes example

Cystic Fibrosis - two alleles that can modify severity pulmonary dysfunction 1. MBL2---mannose binding lectin gene -innate immune system serum factor -binds pathogens and promotes destruction by phagocytosis -lower levels of MBL2 result in worse outcomes for lung disease in CF 2. TGFβ1—cytokine transforming growth factor β -higher levels of TGFβ1 result in worse outcomes for CF -promotes lung scarring and fibrosis after inflammation

study of chromosomes and cell division

Cytogenics:

cytoplasm is divided between the two daughter cells Two new diploid cells are formed

Cytokinesis:

Defects in chromosome " writers": Outcomes:

DNA methylases : DMNTs Chromatin modifiers: HDAC or HAT Incompatible with life---many of these genes operate early in development Neurodevelopmental diseases with intellectual disability ---no reproduction present as sporadic cases

heterochromatin

DNA that is densely packed around histones. The genes in heterochromatin are generally inaccessible to enzymes and are turned off.

quadrivalent allignment meiosis

Derivative chr form Quadrivaent-aligned with Homologous material

Developmental defects: palatal defects conotruncal heart defects (e.g., tetralogy of Fallot,) interrupted aortic arch, ventricular septal defects, vascular rings) hearing loss or abnormal ear exams genitourinary anomalies (absent/ malformed kidney) hypocalcemia (low blood Ca+2 levels) microcephaly (small head) intellectual disability (usually borderline to mild) severe T-cell defects critical region includes about 30 genes occurs in 1/3-4000 births

DiGeorge Syndrome -deletion of 22q11.2

cases are trisomic for chr. 21 ; two maternal homologous 21s and a paternal chromosome 21 after fertilization=47, XY,+21

Down Syndrome

characterized by intellectual and developmental disabilities (IDD) Most common cause of mild to moderate Intellectual disability Also has a characteristic facial appearance: flatten nose and face upward slanting eyes single palmer crease short 5th finger that curves inward widely separated 1st and 2nd toes increased skin creases

Downs Syndrome Trisomy 21, (47,XX,+21)

Individuals with _______ syndrome may have: distinctive malformations of the head and facial (craniofacial) area, such as a prominent back portion of the head; low-set, malformed ears; an abnormally small jaw (micrognathia); a small mouth with an unusually narrow roof (palate) an upturned nose. male or female occurence

Edwards Syndrome (47, XY, +18) trisomy 18

Deep Vein Thrombosis: mortality 10% likely from pulmonary embolism environmental factors risk factors trauma surgery (orthoscopic surgery) malignant disease prolonged immobility oral contraceptive use advanced age Double heterozygotes for FLV allele and prothrombin allele -increased risk of 20 fold

Environmental Interac

help maintain genome stability suppress excess activity of transposons maintain function of centromere and teleomeres

Epigenetic patterns

of histone modification, nucleosome spacing and DNA mehtylation patterns define heterochromatin and euchromatin ---allows specific patterns of gene expression to be established in somatic cells of differentiated tissues

Epigenetic patterns

covers all the changes/alteration of gene expression that are heritable ( without changing DNA sequence) including determination of chromosome function 1. Stably transmitted from one cell generation to next (form of "cellular memory") ex: liver cell and its daughter cells "remember" they are liver cells 2. Epigenetic effects are reversible (reprogramming differentiated cells to iPSCs) 3. Most epigenetic effects involve modifying a) DNA methylation patterns b) histones-- alters chromatin environment and hence c) position of nucleosomes-- gene expression

Epigenetics:

total collection of epigenetic changes across a genome 1. characteristic of individual cell types 2.plastic (changes with state of gene expression): influenced by environment, development, aging etc. 3. relatively stable-many propagated from cell to daughter cells 4. trans-generational transmission 5. mCpG islands in DNA can change with cell cycle 6. Histone changes more dynamic can change within hours

Epigenome:

abnormal chromatin formation at one of more loci in the genome

Epimutation:

(Herpes viridea) Infectious mononucleosis Burkitt's Lymphoma t(8;14) Nasopharyngeal Hodgkin's Lymphoma (??)

Epstein Barr Virus

______ in human genome Distribution varies greatly between chromosomal regions heterochromatic (genetically inert) contains non-coding sequence centromeric regions are also non-coding Highest gene density seen in the sub-telomeric regions (euchromatin) Chromosome 19 and 22 are gene rich Chromosomes 4 and 18 are gene poor Size of genes varies: some with single exon to dystrophin with 79 exons (2.5 Mb)

Estimated 22,000-25,000 nuclear genes

Gene expression is dependent on DNA sequence and regional chromatin structure Ex1: Ex2:

Ex1: genes in heterochromatin (condensed) are not generally accessible to transcription factors (silenced gene) BUT if chromatin structure is relaxed (becomes less condensed) transcription factors can access recognition sequence and activate gene expression Ex2: if an inversion or translocation places a gene sequence in constitutive heterochromatin (permanently condensed near centromere) then gene would be silenced (position effect) Epigenetics marks are heritable

coding sequences

Exon=

That is changing as we learn more about eukaryotic /human DNA. regions show that evolutionary conservation---may play a role in gene regulation

Extragenic DNA

There is non-coding sequence (transcriptionally inactive) in the human genome--- Originally termed "junk DNA" and not attributed a function.

Extragenic DNA

contraction of D4Z4 repeats exposed less repressive chromatin

FSH dystrophy

-colon cancer APC gene product binds to β-catenin Excess β-catenin promotes excessive cell growth APC binds to and inhibits β-catenin

Familial Adenomatous Polyposis Coli (APC)

The more closely two individuals in a family are related -the more alleles they share

Familial Aggregation

one would expect that a disease affected individual would have a greater than expected number of affected family members than that found in general population

Familial Aggregation

similarities among family members for both qualitative and quantitative traits suggests overlapping genotype exposure to non-genetic factors (environment) 1. socioeconomic status 2. local environment 3. dietary habits 4. culture behaviors

Family Studies

-may be shown by multiple miscarriages in a family - apparent reduced fertility

Fetal disorders

LOD Score Analysis=Logarithm of Odds ratio The method is as follows for a complex trait. 1) if the gene(s) for disease are not known; can you link them to a marker on the same chromosome? a) establish a pedigree b) make a number of estimates of recombination frequency c) calculate a LOD for each estimate d) the highest LOD score is the best estimate Θ=recombination fraction for linked genes or unlinked putative markers Θ value between 0≤x≤0.49 Likely Hood Ratio (LR)= (Θrecomb (1-Θnon-recomb) Θ=0.5 Then the LOD score = Z= log10 (LR)

Finding Alleles Contributing to Multifactorial Disease

Highest gene density seen in the sub-telomeric regions (euchromatin) _________ are gene rich ________ are gene poor

Highest gene density seen in the sub-telomeric regions (euchromatin) Chromosome 19 and 22 are gene rich Chromosomes 4 and 18 are gene poor

expansion of CCG repeat abnormal methylation and silencing of FMR1 neurodegeneration disorder -premutation 60-200 repeats

Fragile X

Chromosome Karyotype

G or Giemsa Banding Represents the most common method Chromosomes are treated with trypsin to denature their protein content Trypsin-treated chromosomes are stained with a DNA-binding dye -Giemsa Giemsa staining gives each chromosome a characteristic and reproducible pattern of light and dark bands Light bands=euchromatin"active" gene regions Dark bands=heterochromatin "inactive"

signaling initiated by growth factors may be mediated by membrane associated guanine-nucleotide binding proteins activated by mutation another class of oncogene

G proteins:

inhibit cell proliferation/promote apoptosis of cells with DNA damage p53, RB1, APC, MYC

Gate Keepers:

Categories of TSG:

Gate Keepers: p53, RB1, APC, MYC Caretakers: BRAC1, BRAC2, MSH2, MLH-1, WT-1, NF-1

multiple rounds of DNA replication at a single site (double minute chromosomes)---N-myc in neuroblastoma amplified about 30% Some of these defects can be inherited---seen frequently in "cancer" families

Gene amplification:

deletions are compatible with viability however >2% deletion of a chromosome region in a haploid genome is lethal

General observation:

Example: in CF, pulmonary insufficiency can not be explained by mutant alleles where pancreatic insufficiency can be depending on the location of the mutants in the CFTR gene. Therefore---some other gene may modify the CF phenotype Candidates for modifiers are: MBL2—mannose-binding lectin---a serum protein that binds to carbohydrates present on the surface of many pathogens resulting in phagocytic destruction common alleles in European populations show reduced levels of MBL2 TGFβ1---transforming growth factor beta---alleles that produce higher levels of TGFβ1 are associated with worse outcome for CF may be due to promotion of lung fibrosis and scarring after infection

Genetic Modifiers

In patients homozygous for β-thalassemia who also inherit an α-thalassemia allele frequently have milder disease than the β-thalassemia homozygote alone In this case, the α-thalassemia allele reduces the amount of excess α chain produced and thus reduces the imbalance in Hb produced in the β-thalassemic patient— Here the heterozygote α-thalassemia allele modifies the disease.

Genetic Modifiers

Examination of _____ set of variants (frequently SNPs or dinucleotides repeats) in different individuals to see if any variant is associated with a trait (ex. associated with development of disease) Typically identify small effects correlating with genes The first successful __ (published 2005) linked two SNPs with age-related macular degeneration that were not found in controls

Genome Wide Association Studies (GWAS) genome wide GWAS

is an epigenetic phenomenon where certain genes can be expressed in a parent-of-origin-specific manner.

Genomic Imprinting:

Start: launched in 2010 Goal: characterize 1000 epigenomes in 10 years from different human tissues and individuals Mission: translating discoveries into improved human health Tools: significant practical/technical limitations 1. many cells types not accessible (brain) 2. epigenetic settings in surrogate cell cultures may not reflect natural state 3. need better methods (antibodies) to detect epigenetic marks

Global effort: International Human Epigenetic Consortium (IHEC)

can stimulate tumor cell growth Use normal pathways but where one cell produces a growth factor and then that effects another cell via a receptor for the growth ligand (paracrine mechanism) The tumor cell often secretes the growth factor and expresses the receptor on it's own cell surface (autocrine)---consequently cancer cells become less dependent on external growth factor stimulation and their growth becomes unregulated.

Growth factors and receptors:

if hypoxic conditions induces ______ that interacts with _____ and other cytokines > induces neovascularization of the tumor allowing the size to increase

HIF1 (hypoxia inducible factor 1) vascular endothelial growth factor (VEGF)

AIDS epidemic led to the isolation of two viral agents:

HTLV-1 the first human retrovirus --Kaposi sarcoma associated herpes (KSHV) virus isolated from the recurrent sarcomas seen in AIDS patients but thought to have an independent cause from HTLV-1 Merkel cell polyoma virus---isolated from Merkel cell carcinoma by subtracting human DNA sequences from a tumor transcriptome set. Left with the virus sequences Digital Transcriptome Subtraction (DTS) Merkel cell virus is thought to cause 70-80% of these tumors considered a neuroendocrine tumor found in skin in sun-exposed areas

Robertsonian: Meiosis

Haploid segregation products of chromosomes: meiosis

carries The single set of genes that males acquire from their mother's X chromosome. A genetic occurrence when an organism has only 1 allele for a trait. In humans, males with only one X chromosome.

Hemizygous

originate in bone marrow, lymphatic system and peripheral blood

Hemopoietic/Lymphoid-

Infectious hepatitis Hepatocellular carcinoma

Hepatitis B and C

how much do genetic differences between individuals in a population contribute to the variability of that trait in a population __ the fraction of the total phenotypic variance of a quantitative trait that is due to allelic variation, regardless of mechanism of variation the value of __ varies from 0 to 1 a value of __ suggests that the gene in question is totally responsible for the phenotypic variance in the population studied

Heritability H^2 H^2 1

-repetitive DNA or silencer elements -expands across long distances on Chr. -converts "open" chromatin to condensed transcriptionally silent chromatin -facilitated by communication between nucleosomes

Heterochromatin is formed at nucleation sites

refers to having different alleles at the gene locus on the chr.

Heterozygosity

pathogenic developmental abnormality of enteric nervous system of the gut absence of the intrinsic ganglion cells in the myenteric and submucosla complexes of the colon aganglionic colon incapable of peristalsis -mega colon (above tha aganglionic segment) -severe constipation -symptoms of intestinal obstruction 1/5000 Caucasian infants; 1/2500 Asian infants mutations in RET gene, receptor tyrosine kinase, most common investigations suggest at least 3 loci interacting λsiblings=200 modified expression of multifactorial traits ---reduced expressivity or penetrance

Hirschsprung Disease (HSCR)

failure to develop colonic ganglia-defect in colon motility and severe constipation (dominant) Phenotypic Heterogeneity

Hirschsprung Disease:

Loss of function mutation in RET gene (receptor tyrosine kinase)

Hirschsprung Disease: Other mutations in RET LMNA gene Phenotypic Heterogeneity

HDACs

Histone Deacetylases

refers to having the same allele of a given gene locus on both chr.

Homozygosity

Adult T-cell Leukemia Lymphoma; Hairy Cell Leukemia

Human T-cell Leukemia (HTLV-1; HTLV-2)

are largely unique DNA sequence coding for a polypeptide with a cellular function or in combination with other polypeptide form functional unit such as: enzyme, hormone, receptor, structural or regulatory protein

Human genes

(X linked lysosomal storage disorder ) cells that can make iduronate sulfatase (active normal X) can secrete the enzyme into the cellular space and the cells with the mutant X can export the active enzyme. the penetrance for Hunter's syndrome in heterozygote females is low expected is 50%-50% Contrast with carrier females of fragile X syndrome that show developmental delays but lesser extent than males

Hunter's Syndrome

_______ may be the only completely dominant disease known

Huntingdon's

(immunodeficiency, centromere instability (star formation) and Facial Anomalies Syndrome) very rare autosomal recessive immune disorder facial anomalies: low set ears, epicanthic folds loss of immunoglobulins---susceptibility to infections mutation 20q11.2---Dnmt3b gene

ICF Syndrome

DNMT3B loss of function mutations in methyl transferase

ICF Syndrome

deficiency of one of the DNA methyltransferases (DNMTs) that maintains pattern of genome methylation (centromeric instability, immunodeficiency) Several instability syndromes associated with increased risk of cancer

ICF Syndrome:

restricted binding to cdk4/6---primary function to regulate phosphorylation of Rb critical cell cycle checkpoint (p16/INK4a is also a tumor suppressor mutated frequently in melanoma) over 90% of lung cancers show mutation or dysregulation of cyclin/cdk/Rb pathway

INK4 Family members: p16/INK4a, p15/INK4b, p18/INK4c, p19/INK4d

Paracentric meiosis

If a crossover loop occurs in the alignment of paracentric chromosomes results in: products that are an acentric fragment or dicentric Example: DBCD (acrocentric --no centromere) A *CB*A (dicentric * indicates centromere) A * BCDE normal product A * CBDE inversion product The acrocentric fragment in a zygote fails to undergo mitosis embryo survival unlikely; dicentric chromosomes are unstable and again embryo unlikely to survive In this case survival of an abnormal baby very unlikely

DNA can be heated and the double helical structure comes apart-- the rate of reannealing can be used to predict

If cooled slowly, the strands will re-associate (re-anneal) at a rate that is dependent on unique and repeat sequences contained in the DNA Analysis of the kinetics of human DNA re-association estimate that 60-70% of the human genome is single (low copy number) DNA sequence Remaining 30-40% is estimated to be moderately or highly repetitive DNA sequence that are not transcribed satellite and interspersed sequence DNA

Epigenome can now be interrogated by using ______ Bead chip ("Methylome")—scans 485,000 CpG sites in human genome Aging, risk factor for complex disease, marked by progressive inefficiency in cell, tissue and organ function changes in somatic cells of organs and stem cells that regenerate

Illumina Infinium Human Methylation 450

Situation where the mating is between individuals an isolated/geographically restricted area or for cultural or religious reasons (may have a common ancestor in past few generations) in offspring increases chance of obtaining a mutant allele form both parents Genetic counselors should ask about intra-family marriages and geographical isolation and cultural history

Inbreeding:

the profile of the average green:red ratio of ten chromosomes shows 8p loss and 8q gain in these cells. The bottom right panel shows copy-number losses of 1p, 6q, 11q and 20p, and gains of 12, 13 and 20q in the ML-2 cancer cell line.

Inset:

two main classes make up 30% of human genome

Interspersed Repetitive DNA Sequence

Loss of one chromosome arm with duplication of the other (2 ps or 2 qs) Most likely explanation the centromere Splits transversely rather than longitudinally Most common is isoXq that accounts for 15% of Turner syndrome cases

Isochromosomes

from banded metaphase spread

Karyotype

caused by variety of mitochondrial deletions -primary symptomology reported by Kearns (1965) 1. ophtalmoplegia 2. pigment degeneration of the retina 3. cardiomyopathy -secondary symptoms 1. facial weakness 2. weakness of pharyngeal, trunk and extremity muscles, 3. deafness 4. small stature 5. increased CSF protein 78% of KSS patients have mtDNA deletions in muscle mitochondria Note: caused by mutation in mitochondrial tRNA (leucine-1 gene) MTTL1 BUT some patients show deletion of multiple mtDNA genes

Kearns-Sayre Syndrome:

Chromosome map

Key Features eukaryotic chromosomes are usually linear typical chromosomes =1010 or base pairs in length occur in sets; somatic cells are 2N Genes interspersed along chromosome fewer than 100 to several thousand genes origins of replication about every 100,000 bases centromere contains recognition sites for kinetochore proteins telomeres-specialized sequences at each end repetitive sequences found at telomeres and around centromere but not confined to those regions

mitochondrial respiratory complex defects mutations have been noted in both mtDNA and nuclear encoded genes functioning in the mitochondria respiratory chain Very heterogeneous disease -potential defects in many mitochondrial complexes defects noted in mitochondrial respiratory complexes: mitochondrial complex I-mutations in NDUFA12 (nuclear gene) mitochondrial complex II mitochondrial complex III mitochondrial complex IV (cytochrome c oxidase)—most common deficiency mitochondrial complex V—mitochondrial ATP6 mutation Mutations have also been noted in mitochondria tRNA proteins (MTTV, MTTK, MTTW, MTTL1) Also noted: X-linked recessive and autosomal recessive modes of inheritance (involvement of nuclear genes)

Leigh Syndrome:

proteins that assemble at the centromere and where spindle fibers (microtubules) attach that allows separation of the sister chromatids during mitosis/ meiosis

Kinetochore-

have approximately 19 proteins including: CenH3—a specialized histone Microtubles (tubulins) Motor proteins—dynein and kinesin

Kinetochores

47, XXY or 48,XXXY or XY/XXY mosaic; occurrence 1/500-1000 male births

Klinefelter Syndrome:

-nuclear envelop protein mutations in LMNA are associated with: Emery-Dreifuss muscular dystrophy, a form of dilated cardiomyopathy, Charcot-Marie-Tooth peripheral neuropathy, lipodystrophy and Hutchinson-Gifford progeria Phenotypic Heterogeneity

LMNA gene (encodes lamin A/C)

can be seen on banded chromosomes under the light microscope ---Cru du Chat Syndrome (5p del) and Wolf-Hirschorn Syndrome(4p del)

Large chromosomal deletions:

individual may have children; presence of mutant allele may be masked by death of the parent

Late onset disorder:

Diagnosis based on visual findings (legally blind) significant impact on quality of life patients (90%) have one of 3 identified point mutations in the mtDNA m. 3460G>A, m. 11778G>A or m.14484T>C mutations affect different respiratory chain complex I subunit genes Management: largely supportive, provision of visual aids, occupational therapy Families with known risk: members should be encouraged to avoid alcohol and smoking or other environmental exposures that might exacerbate disease

Leber's Hereditary Optic Neuropathy (LHON)

develops young adult with painless, bilateral subacute visual failure males 5X more likely than females to be affected females with the disease may go on to develop an MS-like illness

Leber's Hereditary Optic Neuropathy (LHON)

---predisposition to cancer/increased life time risk Common types of cancer found: bone, breast, brain Carry germline mutation in p53 ---tumors mutations in both alleles

Li Fraumeni Syndrome

-represent about 5% of genome LINE-1 (L1) > 100,000 copies of a 6000 bp sequence that encodes a reverse transcriptase Both LINEs and SINEs are implicated in inherited disease

Long Interspersed Nuclear Elements (LINEs) --

cells to revert to less differentiated states ---prototype cancer cell then has more flexibility to adapt to changing environment ---cancer "stem" cells ---reversion phenotype---can induce tumor grow

Loss of Epigenetic pattern allows Epigenetic changes allow proto-cancer cells to attain plasticity to escape normal growth controls

Absence of a single chromosome = besides non-disjunction loss of a chromosome can occur during anaphase lag

MONOSOMY

Loss of a chromosome homolog equals

MONOSOMY

Stages of the Cell Cycle

Lots of cellular activity between mitotic divisions=Interphase (G1+S+G2) lasts approx 16-24 hours Neurons (non-dividing) arrest in G0 (gap phase) S=Synthesis phase G2=Gap 2 -relatively short phase -error fixes M=Mitosis-chromosome and nuclear division G1=Gap 1

Leptotene---condensed chromosomes visible Zygotene---synapsis---homologous chromosomes align along a synaptonemal complex Pachytene---each pair of chromosomes becomes tightly coiled=bivalent crossing over (exchange) between non-homologous chromosome may occur--chiasmata Diplotene---chromosomes begin to separate but still attached at chiasmata chromosomes may have 1-3 chiasmata depending on size approximately 40 recombination events/meiosis/gamete---generates diversity Diakinesis---continued separation of homologous chromosomes and condensations

MEtaphase 1 of meiosis 1

___ cells established in culture will proliferate indefinitely => immortalized

Malignant

__________ or __________ if disease X is manifest in tissues then those tissues show disease ---depends on % of cells with diseased X ( and vice versa)

Manifesting Heterozygotes or skewed X Inactivation:

Is not a cycle, there is an end product

Meiosis

Occurs during gamete formation in spermatocytes and oocytes

Meiosis

is different from mitosis (cellular division) Chromosomes are maintained in diploid state in daughter cells from mitosis occurs during formation of gametes effectively occurs in two steps (mitosis is a one step process)

Meiosis

=reductional division derives haploid number chromosomes

Meiosis I

essentially a mitotic cell division with haploid chromosomes

Meiosis II=

chromosomes separate to opposite poles as the spindle tubules contract

Meiotic Anaphase I:

nuclear membrane disappears and the chromosomes aligned on equatorial plate attached to spindle as in mitosis

Meiotic Metaphase I:

each haploid set of chromosomes in two daughter cells =secondary spermatocytes/oocyte

Meiotic Telophase I:

in male the X and Y segments that are homologous (tips of short arms) pair =pseudoautosomal regions

Meiotic prophase I

each chromosome separates into a chromatid =formation of a sperm or ovas

Meoisis II: a mitotic division

Consequently, genetic counselors (or physicians) should advise the parents that there may be a recurrence risk of 3-4% of another child with the same disease ---difficult to estimate because hard to know what % of gametes are mosaic.

Mixed mosaic—

depending when embryonic mutation occurred could be present in both somatic cell lineages and gametic lineages

Mixed mosaic—

is only change in DNA

Methylation

single, di-, tri- and tetra-nucleotide repeats located throughout genome rarely occur in genes but are associated with disease (Huntingdon's Chorea) arise by slip strand mis-pairing or unequal cross-over uses: paternity testing, forensic analysis and tracking alleles in pedigrees

Microsatellite-

the presence of an dominant disease in an affected child from unaffected parents (phenotypically normal and carrier status ruled out) suggests a germline mosaic NOT always a new (spontaneous) mutation in the family. incidence of new mutations is low (1/104-106)

Mixed mosaic—

Other genes that can effect function of an unrelated gene

Modifier Genes

—telomeric -terminal portions of chromosomes (telomerase) maintain integrity of chromosome ends hypervariable-short tandem repeats of a core sequence (DNA fingerprinting)

Mini-satellite

Tandem DNA Repeats

Mini-satellite Satellite DNA Microsatellite-

(16.6 kb, 37 genes) two rRNA genes 22 tRNA genes

Mitochondrial DNA

9% of infertile males (study in Finland and England) found to have CAG loss in PLOG in fertile males CAG repeat was present given role of mitochondria in sperm this was a significant finding

Mitochondrial Depletion Syndromes: Fertility

Alpers Syndrome (4A), MNGIE (4B) Progressive External Ophtalmoplegia (autosomal dominant and autosomal recessive) found in both nucleus and mitochondrial mitochondrial form =PLOG PLOG2 =c-terminal polymerase domain and n-terminal exonuclease domain the exonuclease domain gives the mitochondrial form a proof-reading function and increases the fidelity of mtDNA replication By FISH the PLOG gene maps to 15q24-q26 hypothesized that mutations in the exonuclease function lead to loss of fidelity in mtDNA replication and high frequency of randomly distributed mutations in mtDNA genome -also can show decreased polymerase activity results in mtDNA depletion and lost of mitochondrial function A467T mutation is the most common in mtDN for this condition A (CAG)n=10 repeat also found at 5' end of PLOG mutations here may also account for some cases of the disease

Mitochondrial Depletion Syndromes: DNA polymerase gamma (PLOG):

MELAS-mitochondrial myopathy, encephalmyopathy, lactic acidosis and stroke-like symptoms KSS-Kearns-Sayre Syndrome LHON-Leber's Hereditary Optic Neuropathy NARP-Neuropathy, ataxia, retinitis pigmentosa MERRF-Myoclonic epilepsy with ragged red fibers LSP-Leigh Syndrome

Mitochondrial Diseases

-first characterized in 1984 -affects the nervous system and muscles -signs and symptoms appear in childhood after normal development 1. muscle weakness 2. recurrent headaches 3. loss of appetite 4.vomiting 5. seizures-brain damage can result- (vision loss, movement problems, loss of intellectual functiondementia) -most patients also show lactic acidosis -increase in acidity of blood (vomiting, extreme tiredness, abdominal pain, breathing difficulty mtDNA mutations 1. Complex I: NADH dehydrogenase ---converts O2 and simple sugars energy 2. mtDNA tRNA mutations (MT-TH, MT-TL1 (80% cases), MT-TV)

Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-Like Episodes (MELAS)

-also known as POLIP Syndrome -symptoms appear 2nd-5th decades of life-multisystem disorder caused by mutation in TYMP (thymidine phosphorylase) mutations found in 100% of affected individuals TYMP activity ≤10% of normal in leukocytes---diagnostic test Gastrointestinal tract -poor mobility, pseudo-obstruction with peristalsis leads to malabsorption-weight loss -Neurological peripheral neuropathy and myopathy Most common mitochondrial dysfunction is in respiratory complex IV (COX)

Mitochondrial Neurogastrointestinal Encephalopathy Syndrome (MNGIE):

type of cell division that replicates somatic cells; producing two identical daughter cells cytoplasma and nucleus divide number of chromosomes/nucleus remains the same

Mitosis:

Cell cycle is the "master switch" for cell proliferation---many processes competed in a timely progression and sequence regulation is multifactorial through a set of "checks" and "balances"

Movement through the cell cycle controlled by cyclins and cyclin dependent proteases (CDKs) chromosome segregation (mitosis) forms a cell cycle kinase

Development of cancer = ONCOGENESIS

Multi-step process that results from dysregulation of genes controlling biological processes such as: cell growth and replication sensitivity to cell apoptosis (programmed cell death) maintenance of genetic stability

Fewer congenital malformations result in live births. Almost all chronic adult disorders result in live births, and manifest later. how common?

Multifactorial Disorders (most common)

inheritance is characterized by complex interactions between a number of genes and environmental factors. Some gene may have large contribution that others. a genetic mutation may predispose an individual to disease; other genetic and environmental factors contribute to whether the disease develops a variety of genetic alterations predispose individuals to the same disease genetic heterogeneity For example: risk factors for heart disease high blood pressure hyperlipidemia diabetes type 2

Multifactorial inheritance:

___ code for proteins of similar function ( example hemoglobins) Arise by gene duplication and then divergence away from "exact" function

Multigene family

MLH1 (mismatch DNA repair) germline epimutation abnormal methylation of promoter

Multiple cancers

multiple mtDNA mutations associated with the disease (MTTK, MTTL1, MTTS1, MTTS2, MTTF and MTND5) - variable expression and variable inheritance consistent with mitochondrial disease - clinical spectrum is consistent with heteroplasmy and segregation of mitochondria within daughter cells serum levels of pyruvate and/or lactate are elevated 80-90% of MERRF cases are associated with 8344A>G mutation in mtDNA MTTK tRNA produces multiple deficiencies of enzyme complexes on the respiratory chain 1.NADH-CoQ reductase (complex 1) 2. cytochrome c oxidase (COX) (complex IV) this is consistent with a defect in translating all the mtDNA encoded genes

Myoclonic Epilepsy Associated with Ragged Red Fibers (MERRF):

Why does the risk increase with maternal age?

Non-disjunction in maternal meiosis I Robertsonian translocations - a break between two acrocentric chromosomes near their centromeres with subsequent fusion of their long arms (centric fusion).

Gene _____ negatively regulates ras proto-oncogene Loss of both copies of ___ promotes growth by unregulated ras

Neurofibromatosis Type I (NF-1)

characterized by symptoms mainly affecting the nervous system symptoms begin in childhood or early adult 1. sensory neuropathy tingling , numbness, pain in arms and legs 2. muscle weakness 3. ataxia -problems with balance and coordination 4. vision loss (light sensing cells of retina disappear) mtDNA gene = ATP6 (one subunit of ATP synthase) 70-90% mitochondria carry mutation -makes a protein essential for mitochondrial function O2+ simple sugars ATP

Neuropathy, ataxia and retinitis pigmentosa (NARP):

Error in chromosome separation during either mitosis, meiosis I or meiosis II

Non-Disjunction

involved in intracellular signaling that have the potential to become oncogenic Best characterized example: src family (3 domains SH1, SH2, SH3)—SH1 has kinase activity SH2 and SH3 involved in protein-protein interactions intracellular signaling function---mutations may generate constuitive signaling within cell 2nd example: Bcr-Abl oncogene—chimeric fusion derived from t(9;22) in chronic myelogenous leukemia (CML)—Ph chromosome c-Abl (chromosome 9) is a tyrosine kinase; Bcr (chromosome 22) is a GTPase activating (GAP) protein---fusion protein causes unregulated cell growth by initiating ras signaling---reduces growth factor dependence, alters cell adhesion properties, enhance cell viability

Non-receptor tyrosine kinases:

_________ have a finite capacity to grow and divide a dividing cell completes 50-60 mitotic divisions -then senesce and apoptosis

Normal diploid cells

( approximately 3 x 109 bp) Genes (22,000) Unique single copy DNA Multigene families Classic gene families Gene Superfamilies Extragenic DNA (unique low copy or moderate/highly repetitive) Tandem repeats Satellite Minisatellite DNA telomeric hypervariable Microsatellite DNA Interspersed short interspersed nuclear elements long interspersed nuclear elements

Nuclear DNA

is a gene, coding for a protein, that increases the malignancy of a tumor cell Many ____ are involved in early stages of cancer development and their expression may contribute to the chance that a normal cell develops into a tumor cell, Research indicates that small RNAs 21-25 nucleotides in length (miRNAs) are involved in expression of ____ by down-regulating them.

ONCOGENE oncogenes oncogenes

Multi-step process that results from dysregulation of genes controlling biological processes such as: cell growth and replication sensitivity to cell apoptosis (programmed cell death) maintenance of genetic stability Development of cancer = ONCOGENESIS

ONCOGENESIS

derived from cellular genes (proto-oncogenes) that become dysregulated as a result of mutation contribute to cell proliferation or decrease sensitivity to cell death identified by:

Oncogenes: 1. chromosomal translocation analysis 2. gene amplification studies 3. gene transfer experiments 4. early RNA tumor virus studies

A virus that can cause cancer-first shown by researchers that a chicken cancer could be caused by avian sarcoma leukosis virus (1908) transferred in a cell free extract later confirmed by Peyton Rous ---RSV (rous sarcoma virus) (1910) In 1936, John Bittner showed that murine mammary tumors were transmitted by an agent in the mother's milk (MMTV) Epstein, Achong and Barr isolated Epstein-Barr virus from Burkitt's lymphoma cells human herpes 4 virus more commonly referred to as EB virus---shown to be a a "transforming" virus Hepatocellular carcinoma---associated with both Hepatisis B and C viruses

Oncovirus

distinct phenotypes in different families with mutations in the same allele---impacts correlation of genotype with phenotype and genetic counseling

Phenotypic (or clinical) Heterogeneity:

unregulated hyperfunction of the kinase inherited cancer of thyroid and adrenal glands = multiple endocrine neoplasia (MEN) type 2A and 2B A third group mutations in RET present with both Hirschsprung and MEN Phenotypic Heterogeneity

Other mutations in RET

Mutation in the same gene can present with amazingly different phenotypes

Phenotypic Heterogeneity

The gain of another complete haploid set of chromosomes is called

POLYPLOIDY

___ is a normal gene that can become an oncogene, either after mutation or increased expression. ___ code for proteins that help to regulate cell growth, proliferation and differentiation. ___ are often involved in signal transduction and execution of mitogenic signals, usually through its protein product. Upon activation, it (or its product) becomes a tumor inducing agent, an oncogene.

PROTO-ONCOGENE Proto-oncogenes Proto-oncogenes

Warts and STD genital warts Cervical cancer

Papilloma virus (some)

either entire chromosome or some portion of chromosome =partial _______ Viabledeficits in growth and development

Patau Syndrome Trisomy 13:

regulatory elements that determines transcribed genes from non-transcribed genes vary between cell types; developmental stages Important role in genomic imprinting and X-chromosome inactivation

Pattern of methylation in cis-acting

genes that have more than one discernible effect or a gene that shows effects on multiple aspects of physiology and anatomy

Pleiotrophy:

inheritance "pattern" is the contribution of many genes at different loci, each gene contributing to the trait (small additive effect)

Polygenic Inheritance:

Genomic Imprinting Diseases

Prader-Willi Angelman Beckwith-Wiedemann Silver-Russell Pseudohypoparathyroidism

paternally inherited genomic imprinting example of

Prader-Willi:

regulation of gene expression locks in (stabilizes) patterns of gene silencing -transcription suppressed highly methylated regions of DNA no gene expression

Principle function:

__________examples Vinyl chloride DMN B(a)p Ionizing radiation UV light Chemical agents Drugs (3-MCA)

Pro-carcinogen

autosomal recessive—mutations reported in PLOG 6/24 patients with mitochondrial disease had PLOG mutations in mtDNA in muscle (5 of these patients had PEO, other patient milder symptomology) Apparent spread of PEO to several countries from founder effects in England and Europe

Progressive External Ophtalmoplegia (PEO)

A cellular gene (c-onc) that is homologous to an v-onc sequence found in a virus. It can induce transformation only after being altered (such as mutation or a change of context such as coming under the control of a highly active promoter). generally encode a protein that functions in DNA replication, cell cycle control or growth control during the organism's development.

Proto-Oncogene (refined): Proto-oncogenes

typical cellular genes with typical control sequences (c-onc have introns; v-onc do not) 2) show normal Mendelian inheritance -they are "normal" genes 3) Occupy the same genomic location (no "jumping") 4) There are no LTR sequences (v-oncs always are in an LTR context) 5) v- onc are similar to retrovirus but acquired by human genome long ago 6) c-onc expressed by the cell frequently when the cell is growing, replicating and differentiating normally. They are usually proteins that are involved in growth control. 7) c-onc are highly conserved (important cellular functions) Note: v-onc acquire mutations, hybrid between v-onc protein and cellular fusion

Proto-oncogene Characteristics:

Dyschondrosteosis: skeletal dysplasia (dominant) with forearm deformity and short stature Mutations in SHOX gene that is a homeodomain-containing transcription factor is located on Xp and Yp

Pseudoautosomal Inheritance PAR

DNA sequence that very closely resembles an expressed gene but that is not generally expressed

Pseudogenes

The glucocerebrosidase gene (GBA1) codes for a lysosomal enzyme that degrades glycosylceramide to glucose and ceramide 16 kb downstream of functional GBA1 is a GBA pseudogene (ψGBA), but no promoter so not expressed

Pseudogenes

disease is only present once factors have exceeded a certain threshold Characteristics: 1. underlying scale of continuous variation in liability to development of the disease arises from an interplay of all contributing genetics and environmental impacts 2. The disease is present only when the liabilty exceeds a threshold value

Qualitative Trait: Polygenic Inheritance

Insertion of the retrovirus does not have (v-onc) can be shown to activate c-myc (involved in cell cycle control) or another c-onc from the inserted viral LTR Promoter OR from the viral enhancer (act 5' and 3' over long distances)

RNA VIIRUS

phosphorylated by cyclin complex --inactive This allows restrictions imposed by _ to be removed and cell proliferation to progress

Rb Rb

Expressed only in homozygous individuals (hh)

Recessive (inheritance of the phenotype expression):

Result from mutation that lead to loss-of-function(eg: reduce/eliminate enzyme activity) in most cases 50% loss of wildtype function enough to not cause disease

Recessive (inheritance of the phenotype expression):

λr values would be similar between related members of the proband. MZ twins λr highest λr would then decrease for parent sib pairs or sib pairs λr for more distant relatives smaller yet as allele sharing decreases For Example: MS λr =190 for MZ rwins MS λr=20-40 first degree biological relatives (parents, siblings) MS λr=1 for adopted siblings (same environmental /no genetics shared) conclude most of familial aggregation for MS from shared genetics

Relative Risk Ratio Family Studies

Retinitis Pigmentosa (RP) affected individual are double mutant heterozygotes at two loci ---locus one=photoreceptor membrane protein peripherin ---locus two=photoreceptor membrane protein Rom 1 two protein with overlapping function disease

Retinitis Pigmentosa (RP) Digenic Inheritance pigment clumps in the eye gradual dimming of vision loss of peripheral vision

common cause of visual impairment caused by photoreceptor degeneration with autosomal dominant, autosomal recessive and X-linked forms

Retinitis pigmentosa: Locus Heterogeneity

normal prenatal and neonatal growth; rapid onset of neurological symptoms Loss of milestones between 6-18 months Children become spastic , some autistic, purposeless flapping or arms and legs, 50% cases see seizures (after a couple years deterioration stops and child lives with severe disabilities) Defect-- mutation in MECP2- a DNA binding protein ---usually spontaneous mutation Males that a 47, XXY or 46,X (derX) can survive

Rett Syndrome:

MECP2 X-linked, females; activity binding to methyl CpGs

Rhett

History: 1954 - two female patients in Dr. Rhett's office in Austria noticed with similar "handwashing" behavior, eventually identified 6 girls in his practice 1960: Dr.Hagberg in Sweden noticed female patients with same behavior 1966: Dr. Harberg publishes patient's description (not a mainstream journal) 1983: Rhett syndrome description published in Annals of Neurology (English) 1999: Baylor lab identifies MECP2 gene as causal agent (Methyl binding protein 2)

Rhett Syndrome,

Maternal Age and Down Syndrome

Risk increases with maternal age—most common birth issue

particular type of reciprocal translocation where the breakpoints are located at or near the centromere of two acrocentric chromosomes

Robertsonian translocation:

CREBBP, EP300 protein defect in co-activator of cAMP activity HAT activities changed

Rubinstein-Taybi

Disorders associated with "trans" chromatin structure

Rubinstein-Taybi Rhett α-thalassemia and X-linked mental retardation ICF Syndrome

Sarcomas (connective tissue cancers)

Sarcoma (v-src) (RSV) (chickens, rodents, cats)

originate in mesenchymal tissue (Ex: bone, nervous system, muscle or connective tissue

Sarcoma-

-10-15% of repetitive DNA sequence -clustered around centromeres separated from main DNA as a shoulder of density-gradients =satellite

Satellite DNA

another class of intracellular signaling molecule raf sarcoma mos sarcoma Best studied= raf recruited by ras and then activates a mitogen-induced protein kinases (MAPKs) action invokes activation of transcription factors in nucleus containing "Elk-1" response elements can also activate protein kinase C that signals other kinases to activate -c-jun No pathway acts independently so always "cross-talk" between the ras pathways

Serine-threonine kinases:

Sex ratio differs from expected 1:1 Autosomally transmitted but expressed in only one sex Example: male limited precocious puberty (familial testotoxicosis) males develop puberty at 4+ years of age in some families mutation in LCGR (receptor for leutinizing hormone) mutation activate receptor signaling in absence of hormone heterozygous females show no effect transmission father -> son (confirms autosomal) or carrier female to son

Sex Limited Autosomal Dominant Disorders

A mutation in the HFE gene (hemochromatosis; missense Cys282Tyr) that is homozygous (occurs in approx. 0.5% of European ancestry) Cys282Tyr HFE mutation permits enhanced absorption of iron =hemochromatosis seen more frequently in males than females (10-20% of cases seen in males) hypothesized to be related to females -lower dietary intake of iron -lower alcohol usage -increased iron loss due to menstruation

Sex-Influenced traits

Even though males and females have the same complement of autosomes, an autosomal recessive phenotype can be influenced by the sex of the individual

Sex-Influenced traits

about 750,000 copies make up 5% genome

Short Interspersed Nuclear Elements (SINEs):

These arise after birth in non germ line cells. They occur in ~25% of adults, and sometimes result in cancers or tumors. They are NOT heritable.

Somatic cell genetic disorders:

products of meiosis Sperm= Ova=

Sperm=4 gametes produced Ova= one gamete + polar bodies

resulting from breaking and re-joining of segments in Translocations Deletions Insertions Inversions Ring Chromosomes a different configuration

Structural rearrangements

defined by high resolution prometaphase cytogenetic and FISH microdeletion on 15 p associated with Angelman and Prader-Willi Syndromes

Submicroscopic deletions:

Inversion consequences at meiosis-Pericentric

TRACE CHROMOSOME ARMS Crossover in segment during Meiosis I—inversion loop forms as chromosomes attempt to maintain homologous paring of genes Result: Two complementary recombinants ---one duplication of the non-inverted segment and deletion of the other end The other has the opposite arrangement and the inversion chromosome

Presence of an "extra" chromosome (or piece of chromosome)=

TRISOMY

Gain of one or two chromosome homologs equals

TRISOMY or TETRASOMY

GM2-gangliosidosis (______) -example of an autosomal recessive disorder that is from a genetic isolate (linguistic, cultural or geographical) while the population does not practice consanguinous marriage the incidence of disease is higher in this population Neurological degenerative disorder resulting in death by 6 months in Ashkenazic Jews (northern European descent vs. Sephardic Jews-Mediterranean descent) the carrier frequency is 1/30 (10x higher than a control population of non-Ashkenazic Northern Europeans) French Ancestry in Quebec Canada often have consanguinity present in the pedigree

Tay Sachs Disease

are maintained by telomerase (enzyme) that "caps" ends with a repetitive DNA sequence TTAGGG (many tandem copies) normal cells senesce---approximately 50-60 cells divisions tumor cells---increased telomerase activity implicated in increased cell survival

Telomeres

sister chromatids have separated (independent chromosome) Each group of daughter chromosomes is becoming surrounded by new nuclear envelope 2n chromosome composition of identiacal chormosome sets in each daughter cell

Telophase:

euchromatin

The less condensed form of eukaryotic chromatin that is available for transcription.

HMTs

These proteins add methyl groups, promoting or inhibiting transcription depending on the amino acid affected. X chromosome inactivation and silencing of Hox genes are caused by this.

3:1 Segregation Translocations: Quadrivalent

Three chromosomes can segregate to one gamete with only one chromosome to the other gamete For example, chromosomes 11(A), 22(D) and the derivative 22 (C) segregate together to a gamete that is then fertilized, this results in the embryo being trisomic for material in chromosome 22.

hypercoagulability states Idiopathic Cerebral Vein Thrombosis: clots form in the venous system of the brain catastrophic occlusion of cerebral arteries (no inciting event like infection) occurs in young adults (1/100,000) with high mortality rate (5-30%) missense mutation in clotting factor V Leiden (p. Arg506Gln) -frequency of 2.5% in Caucasian populations -mutant makes protein more stable—exerts clotting effects longer -homozygotes have an 80% higher risk variant in 3' UTR of gene for clotting factor, prothrombin -g. 20210G>A in 3' UTR of gene use of oral contraceptives USE OF ORAL CONTRACEPTIVE

Thrombophilias: Environmental Interactions

Transfer of genetic material from one chromosome to another---occurs in somatic as well as gametic cells—two "breaks" and then exchange of fragments

Translocations

(47, XXX or 48, XXXX)—super females or meta-females, incidence estimated to be 1/1000 female births ; sometimes mother is older

Triple X Syndrome

Robertsonian: Meiosis

Trivalent--- homologous segments pair

In the types of transmission modes presented earlier ---once the responsible mutation occurs then it is STABLE

Unstable Repeat Expansions

accumulation of additional genetic damage after initiating event(s) via more mutations or epigenetic silencing of caretakers that maintain DNA/genome integrity or cytogenetic normality additional aspect: altered expression of control of vascularization that allows local clonal invasion or distant metastasis

Tumor progression:

(45, X) monosomic for X --incidence 1/2000-5000 female births

Turner Syndrome

compares rates of concordance and discordance among identical twins

Twin Studies

Now recognized that there are diseases caused by unstable repeat expansions in a segment of the gene that is responsible for disease phenotype Tandem repeat of three nucleotides: repeat unit=CAG CAGCAGCAGCAGCAGCAGn (poly Q) =CCG CCGCCGCCGCCGCCGCCGn (poly R) In the normal population there a low but variable number of the repeat unit As gene is passed from generation to generation the repeat unit continues to expand beyond the normal range of repeat units causing abnormalities of protein function mechanism is likely "slipped mis-pairing" a DNA replication error Provides an explanation for observed phenomenon and shows germline stability can vary

Unstable Repeat Expansions

Silver-Russell Mechanisms(s) Chr. Loci Genes involved

UPD, duplication translocation, inversion epimutation 7p11.2 11p15.5 several candidates in region biallelic expression of H19 and decrease of IGF2

Pseudohypoparathyroidism Mechanisms(s) Chr. Loci Genes involved

UPD, imprint defect, point mutation 20q13.2 GNAS1

Offspring receives 2 copies of a chromosome from 1 parent and no copies from the other parent. What is the genetic term?

Uniparental Disomy

two copies of chromosome or chromosome region from a single parent. [initially thought UPD would be rare event but since 1988 reported for all chromosomes except 3 and 19) Therefore: a recessive mutation on Chr. 7 in that UPD region was location for CF gene and this regional UPD (homozygosity) accounted for other somatic findings Proposal: UPD causes disease due to disruption of epigenotype and genomic imprinting

Uniparental Disomy:

female patient: 16 yr. age 130 cm, normal IQ suffered from CF and growth hormone deficiency Beaudet group looking for CF gene studied this patient analysis of DNA revealed she was homozygous for multiple polymorphic markers on chromsome 7 including alphoid centromeric repeats excluded hemizygosity and non-paternity analyzed grandmother's DNA (patient's mother deceased) Concluded: child had inherited two identical copies of her grandmother's centromeric chromosome 7 region

Uniparental Disomy: two copies of chromosome or chromosome region from a single parent. [initially thought UPD would be rare event but since 1988 reported for all chromosomes except 3 and 19) Therefore: a recessive mutation on Chr. 7 in that UPD region was location for CF gene and this regional UPD (homozygosity) accounted for other somatic findings Proposal: UPD causes disease due to disruption of epigenotype and genomic imprinting

first identified as a factor secreted from __tumor cells caused normal blood vessels to become hyperpermeable found in almost every tumor type studied---especially high in hypoxic areas __ receptors (FLK1 etc.) found in blood vessels within or near tumor sites __antibodies can suppress tumor growth in mouse tumor models

VEGF—(vascular endothelial growth factor) VEGF VEGF VEGF

Number and bp size of exons and introns is highly Variable Also some large introns have coding sequences with them (gene within gene)

Variable

_______ expression mask disease in a family ______ in the individual---thus only the family member with disease

Variable Sporadic mutation

80% cases from inherited ___ mutation Multiple tumors (brain, kidney etc) in body ____ interacts with HIF1-α ---if mutated transcription of VEGF and PDGF are activated

Von Hippel Lindau Syndrome (VHL)

Robertsonian: MeiosisZygote chromosomes after fertilization

Zygote chromosomes after fertilization

WT-1 codes for gene involved in kidney/gonad development Regulates transcription of PDGF and IGF-1—growth promoters

Wilm's Tumor (WT-1)

Approximately 85-90% of cases of WHS occur as the result of a new deletion in the affected individual ( de novo deletion) ---means that the affected individual's parents did not have any chromosome arrangement that led to the deletion. The chance for recurrence in future pregnancies of a couple that have an affected child is not increased. In the remaining 10-15% of cases, one of the parents of the affected individual carries a balanced translocation.

Wolf-Hirschhorn syndrome (WHS)(4p-)

refers to a condition that is caused by a missing part (deletion) of the short arm (p) of chromosome 4. Missing genetic material in 4 P results in severe developmental delays, a characteristic facial appearance, and may include a variety of other birth defects.

Wolf-Hirschhorn syndrome (WHS)(4p-)

Gender specific ---in the scheme of thing relatively common Female abnormalities -variation in the number of __chromosomes Male abnormalities -variations in __ number

X X and Y

In females this leads to two cell populations ---one X active in one set of somatic cells and the other X active in a second set of somatic cells (Barr bodies in somatic cells) -all females are thus mosaics for two cell populations -effects of disease can be seen depending on how many somatic cells express the -mutant X allele (manifesting heterozygotes)

X Inactivation & Dosage Compensation

In normal females one X in somatic cells is randomly inactivated ---thus equalizing the amount of product expressed for the X genes in each sex

X Inactivation & Dosage Compensation

Characteristics: Affected males with normal mates: No affected sons, all daughters affected offspring of carrier females (males and females equally) have a 50% chance of inheriting disease Affected females are twice as common as affected males. Affected females tend to have milder disease and variable expression of phenotype

X-linked Dominant

X and Y chromosomes determine sex phenotype The 1100 or so genes located on the X are easily detected as _______ and 40% are associated with disease phenotypes (many Autism Spectrum Disorders are X-linked) Males are hemizygous for ))) traits so depending on the allele -they are normal (XH)or affected (Xh) as in Hemophilia A Females have two X's females could be XHXH, XHXh, XhXh 2/3 unaffected, 1/3 affected

X-linked Inheritance X-linked X-linked

Characteristics: Incidence of trait much higher in males than females Heterozygous females unaffected BUT some may express the condition depending on X-inactivation pattern Affected males transmit to all daughters and each carrier daughter has a 50% chance of transmitting to her sons No male to son transmission Carrier females transmit the trait—affected males in a pedigree are related via female relatives A high % of isolated cases are due to new mutations

X-linked Recessive

Considered ___ if regularly expressed in heterozygotes >lack of male to male transmission > all the daughters of affected males affected while none of the sons affected

X-linked dominant

47, XYY "super-males" frequently tall

XYY Syndrome:

Z score is any score of ____ is significant

Z= log10 (likelyhood of genotype/phenotype data assuming linkage) above 3

centromere at terminal end (sometimes have satellites that form

acrocentric---

Tumor cells may produce their own growth factors that bind to receptors on cell surface Result:

a continuous self generated growth signal (autocrine stimulation) that drives proliferation in the absence of normal exogenous stimulation Example: Epidermal Growth Factor Receptor (EGFR) plays a major role in the proliferation of most human epithelial-derived tumors (also associated with poor prognosis) --Makes EGFR a possible drug therapy target

From molecular genomic studies cancer is ____ disease

a genetic gene dysfunction is implicated in initiating and driving cancerous tissue changes heritable cancer syndrome genes can be linked to cancer development analysis and documentation of common mutations in cancer tissue Genomic studies identify changes that are associated with cancer no two cancers will be the same (although the tumor may share some common mutations ) personalized medicine candidate drugs to target specific cellular processes

Recall that chromosomes are made of

a single molecule of DNA complexed with proteins (histones) . Eventually compacted into the cell nucleus.

Threshold level of mutant mitochondria that usually cause disease

above 70% mutant mitochondria usually show disease

Chromatin Structure can be done through

acetylation methylation ubiquination sumoylation phosphorylation

Different versions of the gene at a specific locus are call

alleles

result of different mutations at same locus with related phenotypes=>

allelic heterogeneity

____ pattern is chromosome specific

banding

non-coding intervening sequence

c

Molecular Consequences-Inversions

can cause gene fusions can cause breaks in genes

Important ______ phenotypes: altered cell proliferation invasiveness (metastasis) apoptosis incidence increases with age

cance2

Mutant alleles responsible for an autosomal recessive disease are rare To have an affected child a carrier must mate with another carrier-hence knowledge of ____ is important for calculating disease risk genetic counseling

carrier frequency

Critical effectors of cell death are the ______ (14 family members) Inactive until proteolytic cleavage at aspartic acid residues Appears to be a cascade of activation of different family members effector caspases 3,6,7---specific cleavage of cellular proteins and morphological degradation

caspases

(c-onc)

cellular-oncogene

are the primary constrictions along eukaryotic chromosomes. mediate chromosomal migration during mitosis and meiosis

centromere

cen

centromere

function in cell division where tow daughter chromosomes are held together during mitosis after dna replication

centromrere

These autosomal recessive disorders _____ ---a detailed chromosome study is necessary to establish disorder and an important element of diagnosis

chromosome instability syndromes

CFTR: 7q31.2 Gaucher GBA:1q21

chromosome number arm of chromosome band of arm .specific area

chromosome breaks apart and randomly reassembles, associated with p53 mutations

chromothripsis--

—show high degree of DNA sequence similarity such as rRNAs at nucleolar organizer regions and tRNAs clustered throughout genome

classic gene family

Multigene Family are of two types

classic gene family gene superfamily-

Increasing degrees of abnormality are associated with sequential loss of tumor-suppressor genes from several chromosomes and activation of proto-oncogenes, with or without a concomitant defect in DNA repair. Example: sporadic cancer with DNA repair defects is less common than a cancer without abnormal repair but, when present, may develop along a somewhat different, but parallel, pathway leading to the final common endpoint of malignancy. Multiple lineages carrying somewhat different mutational spectra and epigenetic changes are likely, especially with transition to metastatic disease

clonal evoution

Can have females homozygous for an X-linked disease (inherit X from father and carrier mother with disease X— ex.

color blindness

twins with same disease are "______" if one MZ twin has sickle cell the other will also

concordant

=recognized at birth (may or may not be caused by genetic defect)

congenital disorder

Another characteristic of tumor formation that no single oncogene mutation could transform a normal cell hence the concept of ______ requiring contributions from more than one oncogene

cooperativity

bind and inactivate the cyclin/cdk complexes p21 activated by P53 when DNA damage detected—halts cell cycle for DNA repair

cyclin dependent kinase inhibitor family)

methylation affects the ______ base of dna

cytosene

A ______ of portions of a chromosome results in loss of genetic material at that region---at that region the individual is monsomic for lost genetic material

deletion

del

deletion 46, XX, del(1q21)

Paracentric meiosis

deletion fused chromosome randomly breaks

Prader-Willi Mechanisms(s) Chr. Loci Genes involved

deletion, UPD, Genomic imprinting 15q11-15q13 snoRNAs and ??

Angelman Mechanisms(s) Chr. Loci Genes involved

deletion, UPD, imprint defect, duplication point mutation 15q11-15q13 UBE3A

HDMs

demethylates histones

which replicates mitochondrial DNA is very similar to reverse transcriptase in HIV Consequently antiretroviral drugs that prevent HIV replication by inhibiting reverse transcriptase will also inhibit ______ in AIDS patients. This stops the replication of host mitochondria leading to a decreased number of organelles and a decrease in function. This decreased number of mitochondria/cell results in the development of metabolic acidosis, a very severe toxic effect of the anti-retroviral HIV drugs.

enzyme polymerase gamma (PLOG) POLG (DNA polymerase γ) Acquired Mitochondrial Disease

Genome Sequence Complexity protein coding

enzymes, cell signaling membrane receptors structural proteins

all nucleated cells in an organism have the same DNA content. How do we get hepatocytes and macrophages and renal cells (i.e., differentiated cells) from the same DNA content? How do uncommitted cells in the very early embryo produce increasingly specialized lineages of cells terminally differentiated cells with unique function? How can stem cells (self-renewing cells in micro environmental niches in each organ) terminally differentiation?

epigenetics NOT dependent on DNA sequence that is the SAME for each cell having arisen from fusion of ovum and spermfollowed by mitotic divisions altered programs of gene expression controlled without respect to DNA sequence =>EPIGENETICS

-chromatin status across all chromosomes is fluid determined by: cytosine methylation pattern histone modification pattern nucleosome spacing Environmental signals/perturbations can significantly alter and increase/ decrease gene expression

epigenome

RECEPTOR: heregulin breast carcinoma

erb-B2/HER2/neu

—light stain active genes

euchromatin

Chromosome Karyotype Light bands=

euchromatin"active" gene regions

Genome Wide Association Studies challenges

failure of replicaiton missing heritability statistical testing problems inter-populaiton applicability

Functions of Mitochondria

fattyacyl coa transport--> beta oxidation tca cycle oxidative phosphorylation atp

are natural mosaics because x chromosome is inactivated randomly

females

finding and unraveling the complex interaction in genes and the environmental impacts that contribute to disease and disease susceptibility finding and unraveling the complex interaction in genes and the environmental impacts that contribute to disease and disease susceptibility Genetic Epidemiology Medical Bioformatics Personalized Medicine

finding and unraveling the complex interaction in genes and the environmental impacts that contribute to disease and disease susceptibility Genetic Epidemiology Medical Bioformatics Personalized Medicine

fra

fragile site 46, X,i(Xq)

---have limited sequence homology but are functionally related having similar structural domains such as Human Leukocyte Antigens (HLA) gene cluster on Chr 6 and the T-cell receptor gene with structural homology to Ig genes

gene superfamily

Mitochondria Respiratory Complexes

genes from mitochondrilal DNA and chromosome dna

Diseases can show phenotypic variation although similar=>

genetic heterogeneity

the individual -due to new mutations and never enter population the affected individual is an isolated case in a pedigree If fitness is normal the autosomal dominant mutation is carried in family and population or age of onset can be late and pedigree shows multiple affected individuals

genetic lethal

multifactorial traits can be influenced by ______________ and __________

genetics and enviornmental factors

epigenetics chages associated with gene activity

genomic mediated histone changes ncRNA mediated hisotne changes ncRNA mediated genomic changes

Knudson- Tumor Gene Suppressor Two Hit Hypothesis

hereditary suppressor cancers were inherited as one faulty gene sporadic needed 2 hits or mutatiosn

dark staining non-coding DNA

heterochromatin—

parent passses on one copy of each homolog (non-disjunction in meiosis I)

heterodisomy

sister chromosome

identical chromosomes

Main viruses associated with human cancer are:

human papilloma viruses hepatitis B and C viruses Epstein-Barr virus human T cell lymphotropic (HTLV) virus merkel cell polyoma virus kaposi sarcoma associated virus (HHV-8)

(vitamin D resistant rickets) impaired ability of kidney tubules to reabsorb PO4- (female hets less affected)

hypophosphatemic rickets

Beckwith-Wiedemann Mechanisms(s) Chr. Loci Genes involved

imprint defect, UPD,11p15.5 duplication, translocation point mutation 11p15.5 IGF2, CDKN1C

Because of X inactivation in females almost all X-linked dominants are

incomplete

An ______ is a two-break rearrangement within a single chromosome where the segment is reversed in position frequently occurs in cancer cells

inversion

inv

inversion 46, XX, inv(9p12q12)

i

isochrome 46, X,i(Xq)

parent passes on two coppies of hte same chromosome (non-disjunction from meiosis II)

isodisomy

dineinin and kinesis

kinetochore spindle fiber

result of mutation at a different loci with overlapping phenotype=>

loci heterogeneity

A ___ designates the position or location of a gene sequence on a chromosome

locus

q arm

long arm of chromosome, grande arm

multifactorial inheritance curve

low but increased risk for family members of affected persons to the general population risk for mor distant relatives consequence: one or very few affected persons in a family precludes a classical pedigree analysis for mendelian traits

nucleolus of interphase chromosome -

many copies of rRNA

Most aneuplodies are maternal/paternal in origin

maternal

Studies show that children with autosomal trisomy inherited additional chromosome copy during

maternal meiotic division

Affected children over the threshold for disrupted function BUT each child will have different degree of heteroplasmy

maternal transmission Outcomes of mitochondria (maternal only) inheritance

mitochondrial inheritance

maternal transmission Outcomes of mitochondria (maternal only) inheritance

nondisjunction in meiosis 1 vs meiosis 2

meiosis 1 left meiosis 2 right

error in meiosis where gamete contains BOTH homologs of one chromosome pair

meiosis I Non-Disjunction error

error in meiosis where gamete contains two copies of one homolog

meiosis II Non-Disjunction error

located near center of p and q arms

metacentric---

One class of gene/protein are secreted or anchored in cell membranes that seem to participate in --___ not normally expressed in adult cells but are over-expressed in tumor cells --Tissue Inhibitor of_____ increased incidence of metastasis in mouse tumor model --expression of MPP-e in normal mammary cells led to invasive tumors

metastasis are the matrix metalloproteins (MPPs) MPPs Matrix Metalloproteinase (TIMM-1)

Zygote changes in Epigenome

methylation increases and decrease to reprogram genes Ova and sperm are differentiated cells with different epigenetic marks---zygote gradually reprogramed erasing inherited epigenetic marks by blastocyst stage cells are pluripotent (inner cells mass)

Unorthodox features and apparently widespread functions 22 nt small RNAs synthesized from DNA Many roles elucidated to date but very "hot" area of research ___ active in many cellular functions: Ex: organogenesis, apoptosis, cell regulation and tumorigenesis ("oncomirs")

miRNA

-microRNAs many roles ---full extent of function still being elucidated (next slide)

miRNA--

Translated c-myc protein often contains some

of virus protein--- one LTR may be lost---production of a fusion protein with oncogenic function

Besides the nuclear DNA each cell has several thousand _______ with their own DNA _______

mitochondria (mtDNA)

Estimates are that 1 in 4,000 children in the United States will develop _____ disease by the age of 10 years. Up to 4,000 children per year in the US are born with a type of mitochondrial disease. Because mitochondrial disorders contain many variations and subsets, some particular __ disorders are very rare. There are also nuclear genes that provide ___ proteins and these can also have mutations and convey mutant protein to ____ and generate dysfunction

mitochondrial mitochondrial mitochondrial mitochondria

genetic informaiton that can be used in the mitochondria

mitochondrial dna in the mitochondria nuclear genes in the chromosomes

15% of diseases result of mutations in mitochondrial genome >60% of disease result from nuclear gene mutations that produce proteins that function in mitochondrial metabolic pathways remainder are acquired mitochondrial conditions (drugs, infections, environmental) Subclass of disease with neuromuscular deficiency =

mitochondrial myopathy

is a cell cycle is not a cell cycle

mitosis meiosis

In developing fetus, autosomal ________ almost always fatal spontaneous abortion

monosomy

Non-disjunction has also been documented to occur in very early zygotes during mitosis ---result is an embryo with two cell types =

mosaicism

/

mosaicism 46,XY/47,XXY

encodes 37 genes -two types of rRNA + 22 tRNAs and 13 subunits of enzymes (cyt b and cytochrome oxidase) involved in energy production using oxidative-phosphorylation

mtDNA mitochondria

is maternally inherited so ________diseases show a maternal inheritance pattern.

mtDNA mitochondria

Cancer is a ______ process requiring incremental changes during it's development Tumor cells typically exhibit uncontrolled growth compared to normal cells Research has defined phenotypic differences between normal and cancer cells basis for the neoplastic behavior of tumor cells

multi-stage

Examples of ________ Alzheimer's disease/ cardiovascular disease/ some cancers/ neural tube defects during fetal development/ Schizophrenia/ Insulin dependent Diabetes (type 2) cleft/lip palate

multifactorial disorders

congenital malformations-- cleft lip/ palate con

multifactorial disorders

inheritance controlled by many genes plus the effects of the environment. clinical clue: one organ system affected

multifatorial inheritance

Symptoms Mitochondrial Disease

nervous system-- seizures skeletal muscle-- weakness liver-- drug toxicities kidneys -- drug toxicity ears eyes --neuropathy heart digestion endocrine

does acetylation have to cover the entire gene for it to be silenced?

no

Notation system for chromosome abnormalities:

normal male or female kryotype- 46, XY or 46, XX male with a trisomy 21 (Down's Syndrome)- 47, XY+21 female with Cri du Chat syndrome (loss of p arm on chr. 5)-46,XX,del 5p Translocation : 46, XY,t(2;4)(p23;q25) + or -: sometime used to denote gain or loss a region

Cross talk between Mitochondria and Nucleus

occurs between transport TOM TIM COMPLEX PROCESS LOOK AT PPT 15 slide 5

micro rna deadenylation

of mrna

micro rna degredation

of mrna

=inversion does not involve the centromere

paracentric inversion

= inversion includes the centromere

pericentric inversion

Examples of _____ characters height, weight intelligence skin, eyes and hair color blood pressure

polygenic

Non coding regions have significant variability - result of mutation or random alterations in DNA; when two or more sequence variants are present in a population with a frequency greater than 1%, it is said to be a

polymorphism

Rarely seen in humans—all are non-viable or die shortly after birth Human________ multiples of ___ Chromosome Number ___ triploidy ___ tetraploidy

polyploidy 23 69 92

These a ________—like Fragile X ---where there is a characteristic cytogenic abnormailty

rare single gene syndromes

Initiation Phase Decision/effector phase Degradation/Execution Phase

pre mitochondria mitochondria post mitochondria

immediate cause of disease, chemical or environmental insult that changes DNA methylation or histone acetylation

primary epimutation:

(three family members H-ras, K-ras, N-ras) Ras protein functions in cell proliferation, cell survival, and remodeling of the actin Cytoskeleton

prototype member=ras oncogene N-ras GTPAse function carcinomas: genital-urinary, thyroid melanoma K-ras GTPase function leukemias, colon, lung cancers H-ras GTPase function melanoma, lung, pancreas cancers

Genome Sequence Complexity No Known Function

pseudogenes, repeated centromeric sequences transposable elements (LINES,SINES, Alu), Variable Number Tandem Repeats (VNTRs) minisatellites (15-50 bp repeats) microsatellites (2-6 bp repeats)

Genome Sequence Complexity RNA coding

rRNA genes (nucleolar organizing region)

tumor suppressor genes have a ____ effect

recessive, you must lose both pairs

Genome Sequence Complexity non-protein coding

regulatory sequences and microRNAs

MeCp2 Involved in Cholesterol Metabolism?

rhett's syndrome maybe

can be created when a strand break occurs at both ends of the same chromosome---these "sticky ends" retain the central DNA portion and stick to form a ring Material from ends is deleted so a ring chr. can have serious consequences Rings are unstable in mitosis and only some somatic cells may retain them; The other cells will be monosomic for the lost ring

ring chromosome

r

ring chromosome 46, XY, r(21)

in a gene that controls epigenetic processes such as proteins that acetylate chromatin or a protein acting as a trans-regulator

secondary epimutation:

a trait/gene on an X or Y chromosome=

sex-linked inheritance

p arm

short arm of chromosome, petit arm

Growth Factor: platelet derived growth factor fibrosarcoma, glioma

sis

During cell division DNA is maximally contracted and can see chromosome structure not normally evident

sister chromatids (DNA replication) Centromere region-chromatids join at central core—consists of repetitive DNA responsible for chromosome movement Centromere divides chromosomes into p and q arms

pseudogene chromosome Distribution in human genome

spread very well throughout the entire genome, some blank spaces

centromere in intermediate position

submetacentric—

Immunologlobins are an example of a(n)

super family

The two products of the CDKN2A gene This gene (also known as MTS and INK4A) encodes two completely unrelated proteins. CDKN2A, or p16INK4A, is transcribed from exons 1α, 2 and 3, and ARF, or p19ARF, from exons 1β, 2 and 3 - but with a different reading frame of exons 2 and 3. These two gene products are active in cell cycle control> two genes could be mutated by one event

they are separated by intron exon spliing

t

translocation 46, XY, t(2;4)(q21,q21)

Most _____ are lethal conditions-approx. 40% of spontaneous abortions harbor an acrocentric chromosome ______= examples include trisomy 13, 14, 15

trisomies trisomy

most spontaneous abortions are caused by

trisomy

Patau Syndrome-

trisomy 13 viable

Rb and p53 are _______ genes

tumor suppressor

Cause of NON-DISJUNCTION---

unclear-- one explanation favors aging of primary oocyte (these can be inactive from birth to around 50 yr.) activated as oocytes needed correlations between maternal age and trisomy 21, 13, and 18 suggested that errors in meiosis prophase chiasmata as age advances may cause susceptibility to non-disjunction

are chromosomes evenly or unevenly populated with genes

unevenly populated

Repair of mitochondrial disease

use mitochondria from healthy person and non mitochondrial genome from healthy person to get rid of mitochondria diseas

---slowly transforming (inserts near a cellular proto-oncogene and viral promoter drives inappropriate cell expression)--- acutely transforming (v-onc expressed immediately in cellular host)

viral oncogenes (v-onc)

Translocations allignments occurs with

with Robertsonian translocation

can environmental factors predispose patients to alzheimers prefvalence

yes

Banding pattern of Chromosome Karyotypes, can they change over time

yes, different genes will be turned on vs turned off at different times

ATRX Xq13; ATRX essential for survival of coritcal neurons

α-thalassemia and X-linked mental retardation

deletion of locus control region (LCR) leads to decreased globin expression

αδβ- and δβ- thalassemia

Disorders associated with "cis" chromatin structure

αδβ- and δβ- thalassemia Fragile X FSH dystrophy Multiple cancers

These ______ are thought to arise in two ways duplication event inserted in genome but inactive due to mutations in coding or regulatory elements of the gene insertion of a cDNA sequence (action of reverse transcriptase or a naturally occurring mRNA) without promoter sequences for expression

ψ genes pseudogenes