Genetics Chapter 6: Pedigree analysis, applications, and genetic testing

What is hemophilia?

-X-linked recessive disorder -defect of blood clotting factors

What is Huntington's disease?

-autosomal dominant -progressive degeneration of nervous system, dementia, and early death

What is achondroplasia?

-autosomal dominant -Dwarfism associated with the defects in the growth of the long bones

What is brachydactyly?

-autosomal dominant condition -malformed hands with shortened fingers

examples of X linked recessive traits?

-color blindness and hemophilia -muscular dystrophy (duchenne and Becker)

what type of condition is hypercholesterolemia?

-considered to be an autosomal dominant -an inherited disease in which blood cholesterol is greatly elevated owing to a defect in cholesterol transport.

what are some examples of autosomal dominant traits?

-hypercholesterolemia -marfan syndrome -Waardenburg syndrome -achondroplasia

what are some examples of x linked dominant traits?

-hypophosphatemia

what is adermatoglyphia (ADG)?

-in which fingerprints are completely absent; this condition is inherited as an autosomal dominant trait.

What is Waardenburg syndrome?

-is inherited as an autosomal dominant trait. -The syndrome is characterized by deafness, fair skin, visual problems, and a white forelock. -Partial albinism esp a 'White Forelock' of hair ,Deafness ,Unibrow

characteristics of CF

-mucus production -lung infection -mucus blocks the ducts

What is an amniocentesis?

-procedure for obtaining fetal cells for genetic testing

what are examples of autosomal recessive traits?

-sickle cell -cystic fibrosis

adoption studies and obesity

-studies demonstrate that obesity has a genetic influence. -overweight biological parents tend to have overweight children -there is no consistent association between the weight of children and that of their adoptive parents

What is muscular dystrophy?

-x linked recessive -genetic disease associated with progressive degeneration of muscles

what are finger prints made of?

Epidermal ridges or dermatoglyphic patterns

How could you distinguish between an autosomal recessive trait with higher penetrance in males and an X-linked recessive trait?

X-linked recessive traits are only passed to sons from mothers, not from fathers.

what is a proband?

a person serving as the starting point for the genetic study of a family

Autosomal recessive traits often appear in pedigrees in which there have been consanguine mating, because these traits...?

appear only when both parents carry a copy of the gene for the trait, which is more likely when the parents are related.

What is Ehlers-Danlos syndrome?

autosomal dominant -connective tissue disorder, elastic skin, loose joints

What is hypercalcemia?

autosomal dominant -elevated levels of calcium in blood serum

What is adult polycystic kidney disease?

autosomal dominant -formation of cysts in the kidneys, leads to hypertension, kidney failure

what is crouzon syndrome?

autosomal dominant, mutation in fibroblast growth factor receptor 2 -defective development of mid face region, protruding eyes, hook nose

what is the importance of ultrasonography?

can be used to detect some genetic disorders in a fetus and to locate the fetus during amniocentesis and chorionic villus sampling.

what happens during hypercholesterolemia?

in this condition the gene that encodes for LDL receptors is defective, this causes a decrease in LDL receptors -LDL particles can't bind to receptors and get into the cells so there is an increase in blood cholesterol levels

What is chorionic villus sampling(CVS)?

is another procedure for obtaining fetal cells for genetic testing

The two types of twins are

monozygotic dizygotic

twin studies and asthma

studies have shown that asthma is caused by a combination of genetic and environmental factors.

true or false: autosomal dominant traits appear equally in males and females

true, affected people have at least one affect parent

true or false: an affected male does not pass the trait to his sons in an X linked recessive trait

true, but an affected male can pass the allele to his daughter who will be unaffected -once the daughter has children or a son he will have condition

true or false: autosomal recessive traits tend to skip generations

true, traits more likely to appear among progeny of related parents

true or false: affected males pass all x linked dominant traits to their daughters and none to there sons

true; affected females ( if heterozygous) pass the trait on the about half of their sons and about half of their daughters

what conditions can geneticist often use pedigrees to study inheritance and characteristics of humans?

•Autosomal dominant traits •Autosomal recessive traits: •X-linked recessive traits •X-linked dominant traits •Y-linked traits

Genetic Discrimination and Privacy

•Many new genetics tests •1970s: African Americans carrying sickle-cell trait had difficulty finding employment and health insurance •Genetic Information Nondiscrimination Act

what are Mitochondrial Inheritance?

•Mitochondria (and genetic disorders caused by mutations in mitochondrial genes) are maternally inherited •Mitochondria are transmitted from mothers to all their offspring through the cytoplasm of the egg

Maternal Inheritance: Mitochondrial Genes

•Mitochondria:Cytoplasmic organelles that convert energy from food into ATP (ATP powers cellular functions) -Carry DNA for 37 mitochondrial genes •Genetic disorders in mitochondrial DNA are associated with defects in energy conversion

Interpreting Genetic Testing

•More than a thousand genetic tests available •Complicated by several factors: -Some diseases caused by numerous mutations -Incomplete penetrance and environmental factors

What is a pedigree?

•pictorial representation of a family history; a family tree that outlines the inheritance of one or more characteristics.

Concordance

•the percentage of twin pairs that are concordant for a trait.

Concordant trait

•the trait shared by both members of a twin pair

what is the numbering system used in pedigrees?

-Each generation is identified by a Roman numeral -Each individual within a generation is identified by an Arabic number (regular number) -Proband: The first affected family member who seeks medical attention for a genetic disorder

CV effects of marfan syndrome

- weakens connective tissue around the base of the aorta

What is hypophosphatemia?

-An X-linked dominant disorder that causes low phosphate levels in blood and skeletal deformities

What is Marfan syndrome?

-An autosomal dominant genetic disorder that affects the skeletal system, cardiovascular system, and eyes -systemically affecting connective tissues. -Most commonly skeletal, cardiac, and ocular.

What is sickle cell anemia?

-An autosomal recessive disorder -Produces abnormal hemoglobin (blood transport protein)

cystic fibrosis (CF)

-An autosomal recessive disorder that is present at birth and affects both the respiratory and digestive systems. -CFTR protein controls the movement of chloride ions across the plasma membrane -human chromosome 7

Examples of genetic diseases and disorders that can be detected prenatally and the techniques used in their detection

-Chromosome abnormalities -Cleft lip and palate -Cystic fibrosis -Dwarfism -Hemophilia -Lesch-Nyhan syndrome -Neural-tube defects -Osteogenesis imperfecta -Phenylketonuria -Sickle-cell anemia -Tay-Sachs disease

what human and biological features makes studying Genetics in Humans Constrained?

-Controlled mating not possible in humans -Long generation time -Small family size

Characteristics ofDuchenne Muscular Dystrophy

-Dystrophin proteins that normally stabilize the muscle cells during contraction are defective -Plasma membranes are torn apart by muscle contraction, causing death of muscle tissue -child with this condition can't get up normally

Common reasons for seeking genetic counseling

1. A person knows of a genetic disease in the family. 2. A couple has given birth to a child with a genetic disease, birth defect, or chromosome abnormality. 3. A couple has a child who is intellectually disabled or has a close relative who is intellectually disabled. 4. An older woman becomes pregnant or wants to become pregnant. There is disagreement about the age at which a prospective mother who has no other risk factors should seek genetic counseling; many experts suggest that it should be age 35 or older. 5. Husband and wife are closely related (e.g., first cousins). 6. A couple experiences difficulties achieving a successful pregnancy. 7. A pregnant woman is concerned about exposure to an environmental substance (drug, chemical, or virus) that causes birth defects. 8. A couple needs assistance in interpreting the results of a prenatal or other test. 9. Both prospective parents are known carriers for a recessive genetic disease or both belong to an ethnic group with a high frequency of a genetic disease.

x linked dominant traits

1. Both males and females are usually affected; often, more females than males are affected. 2. Does not skip generations. Affected sons must have an affected mother; affected daughters must have either an affected mother or an affected father. 3. Affected fathers pass the trait to all their daughters. 4. Affected mothers (if heterozygous) pass the trait to half of their sons and half of their daughters.

steps of chorionic villus sampling (CVS)

1. CVS can be performed early in pregnancy 2. under ultrasound guidance, a catheter is inserted through the vagina and cervix and into the uterus 3. where it is placed into contact with the chorion the outer layer of the placenta 4. suction removes small piece of the chorion 5. cells of the chorion are used directly for many genetic tests, and culturing is not required (chemical analysis, dna analysis, and chromosomal analysis)

Pedigree characteristics Y-linked traits

1. Only males are affected. 2. Passed from father to all sons. 3. Does not skip generations.

what is an autosomal dominant trait?

1. Usually appears in both sexes with equal frequency. 2. Both sexes transmit the trait to their offspring. 3. Does not skip generations. 4. Affected offspring must have an affected parent unless they possess a new mutation. 5. When one parent is affected (heterozygous) and the other parent is unaffected, approximately half of the offspring will be affected. 6. Unaffected parents do not transmit the trait.

what are autosomal recessive traits?

1. Usually appears in both sexes with equal frequency. 2. Tends to skip generations. 3. Affected offspring are usually born to unaffected parents. 4. When both parents are heterozygous, approximately onefourthof the offspring will be affected. 5. Appears more frequently among the children of consanguineous marriages.

what are X linked recessive traits?

1. Usually more males than females are affected. 2. Affected sons are usually born to unaffected mothers; thus, the trait skips generations. 3. Approximately half of a carrier (heterozygous) mother's sons are affected. 4. Never passed from father to son. 5. All daughters of affected fathers are carriers

what are the steps of LDL particle transport in normal individual?

1. an LDL particle attaches to an LDL receptor on the cell surface 2. and moves into the cell 3. in the cell the LDL particle is broken down 4. cholesterol is released for use from the cell

characteristics of cytoplasmically inherited traits

1. present in males and females 2. usually inherited from one parent, typically maternal parent 3. reciprocal crosses give different results 4. exhibit extensive phenotypic variation, even within a single family

steps of an amniocentesis?

1. under the guidance of ultrasound, a sterile needle is inserted through the abdominal wall into the amniotic sac 2.small amount of amniotic fluid is withdrawn through the needle 3.amniotic fluid contains fetal cells which are separated from the amniotic fluid 4. cells are cultured 5.test are performed on the cultured cells

A trait exhibits 100% concordance in both monozygotic and dizygotic twins. What conclusion can you draw about the role of genetic factors in determining differences in the trait?

Both genetic and environment factors are important

What is camptodactyly?

Causes bent, immobile little fingers. Its inherited as am autosomal dominant trait. -Shows less than complete penetrance. -Shows varying expressivity.