quiz 4?
dosage compensation in worms HERMAPHORDITE - XX MALE - X
-downregulation of both hermaprodite Xs by 1/2 -involves SMC proteins, condensins, or condensin-like normally involved in chromosome chondensation in mitosis -Smchd 1 involved in mammalian dosage compensation is an SMC protein
Epigenetic modifications can occur during?
-early stage of embryogenesis -spermatogenesis (sperm formation) -oogenesis (egg formation)
dosage compensation in files FEMALE - XX MALE -XY
-upregulated of male X -involves long noncoding RNAs, roX1 and roX2 -involved histone acetyltransferases -involved RNA/DNA helicase -involved creation of an active nuclear -involved creation of an active nuclear compartment, with enrichment of transcription factories -mammals- upregulation (controversial) involves a long noncoding RNA (XACT), histone acetyltransferase (homolog of same fly HAT)
X-chromosome inactivation (XCI)
Female mammals equalize the expression of X linked genes by turning off one of their two X chromosomes. This process is known as _________________
Based on this pedigree which pairs of family members listed below share mitochondrial DNA? Choose All That Apply
I-1 and III-6 II-1 and III-3
What is true of the ICR (imprinting control region) of a gene?
It is methylated in the egg or sperm but not in both The methylation occurs on a cytosine base located within the ICR
What are common shared characteristics of eukaryotic cells?
Linear DNA strands that interact with histone proteins A cytoskeleton of microfilaments and microtubules DNA within a membrane bound organelle Mitchondria that contain DNA unique from that found in the nucleus
If a reciprocal cross involved a female with the genotype pp and a male with the genotype Pp. Then in the initial cross the female's genotype was_____ and the males genotype was _____
Pp pp
What type of molecule is the functional product of the Xist gene?
RNA that does not code for a protein
sex linked
gene located on the X or Y chromosome -non autosomal
In order for a human female to display a recessive sex-linked trait what must be true?
her father must display/express the trait and her mother could just carry the trait
What separates during the first division that occurs in Meiosis?
homologous pairs of chromosomes
Where would you find the X-inactivation center in a human genome?
on the X chromosomes
The mechanism of XCI, also known as the Lyon hypothesis
pic
According to recent findings, there are more than 36 genes involved in type-2 diabetes and each of these genes contribute to the increased risk to developing type-2 diabetes. What is this is an example of?
polygeny
In flowering plants (Angiosperms), chloroplasts are inherited which parent?
the plant that produces the egg
Both Angelman syndrome (AS) and Prader-Willi syndrome involve a small deletion in chromosome 15_____. If the deletion is inherited from the female______, it leads to AS. If the deletion is inherited from the male_______, it leads to PWS.
true
For each of the following, indicate the number of Barr bodies that will be present in the cell: For each of the following, indicate the number of Barr bodies that will be present in the cell: Turner Syndrome (X0): 0 Triple X Syndrome (XXX): 2 Klinefelter Syndrome (XXY): 1
true
In dosage compensation, the difference in gene dosage is compensated for at the level of gene expression
true
X-inactivation center (Xic)
Although the genetic control of XCI is not entirely understood at the molecular level, a short region on the X chromosome called the ___________________ is known to play a critical role
What is the molecular explanation for genomic imprinting?
DNA methylation-the attachment of a methyl group onto a cytosine base-is a common way that eukaryotic genes may be regulated. Research indicates that genomic imprinting involves an imprinting control region (ICR) that is located near the imprinted gene.
Match the mechanism of dosage compensation with the correct organism in which it occurs
In XX individuals one chromosome is inactivated -humans In XX animals expression of X-linked genes on both chromosomes is ~50% -C.elegans Hemizygous individuals express most sex linked genes at 1/2 the level of non-hemizygous individuals -birds in males the expression of X-linked genes is doubled -drosophila
Dosage Compensation
Mechanism in which X chromosome inactivation equalizes gene expression between males and females.
A female mouse that is Igf2 Igf2- is crossed with a male that is Igf2 Igf2- . What is the predicted outcome of this cross?
NOT -75/25 NOT-all normal NOT- all dwarf
In genomic imprinting, when does marking of a gene occur?
NOT -embryogenesis maybe? - during gametogenesis
Coleus is a flowering plant (Angiosperm) with variegated leaves. If a female plant with green and red chloroplasts is crossed with a male plant with only green chloroplasts what are the possible phenotypes of the leaves of the offspring?
Some all red, some all green and some a mix of red and green
All phenotypic variablity is a result of genetic variability
false
The term __________________ refers to an analogous situation in which a segment of DNA is marked, and that mark is retained and recognized throughout the life of the organism inheriting the marked DNA. Genomic imprinting happens prior to fertilization; it involves a change in a single gene or chromosome dur-ing gamete formation.
genomic imprinting
If two alleles for a trait display incomplete dominance then in the F1 generation a 1:2:1 ratio will be seen in?
genotype and phenotypes
In mice, the copy of the Igf2 gene that is inherited from the mother is never expressed in the offspring. Why?
it is not transcribed in the somatic cells of the offspring
doasge compensation
mammals- inactivation of one X in females (only one active x chromosome in male and female cell) worms- inactivation of both x chromosomes in hermaphrodites by half (hermaphroite XX male X) files- UNREGULATION of single x chromosomes in males (female XX and male XY)
upregulation of active X in mammals
mammals- inactivation one X in females, upregulation of active X in males and females
Which of the following statements about genomic imprinting is accurate?
monoallelic expression of a gene in offspring differential gene expression (maternal vs. paternal copies) in offspring
If a female inherits an unmethylated gene from her mother and a methylated gene from her father what will happen during gametogenesis?
the methylation of the paternal gene will be erased and not be reestablished after gamete formation
If a trait displays a maternal effect, then when a heterozygous dominant female is crossed with a homozygous recessive male what phenotype will the offspring display?
they will all display the dominant phenotype
If a trait displays a maternal effect, then when a homozygous dominant male is crossed with a homozygous recessive female what phenotype will the offspring display?
they will all display the recessive phenotype
Place the three stages of process of genomic imprinting in order.
2-maintenance of imprint in embryogenesis and adult somatic cells 1-establishment of the imprint during gametogenesis 3-erasure and reestablishment of imprint in germ cells
In the pedigree below, individual I-1 has Leber hereditary optic neuropathy (LHON), an inherited form of vision loss caused by a mutation in mitochondrial DNA. Which members of her family will also inherit LHON? Choose All That Apply
III-1 II-3 II-2 II-4
In wildtype individuals the gene for AS is methylated (inactivated) in the Incorrect answer: 15 chromosome. In wildtype individuals the gene for PWS is methylated (inactivated) in the Incorrect answer: 15 chromosome. Deletion of the AS gene from the Incorrect answer: UBE3A chromosome results in Angelman syndrome, while deletion of the PWS gene(s) from the Incorrect answer: SNRPN chromosome results in Prader-Willi syndrome.
INCORRECT
Which of these pieces of evidence provides support for the endosymbiotic theory?
The sequences of certain genes related to mitchondrial function within the nucleus are more similar to bacterial genes Modern chloroplasts and mitochondria have lost most of the genes found in their suggested ancestral bacteria Mitochondria and chloroplasts have the ability to self-replicate something no other eukaryotic organelle can do
What is true of human mitochondrial diseases?
The symptoms of mitochondrial diseases often vary widely in a given family Mitochondrial mutations can occur in somatic cells and accumulate with age Transmission of inherited mitochondrial diseases follows a maternal inheritance pattern
sex limited
When expression of a gene depends on the sex of the individual. -autosomal -both sexs carry the alleles (eg epigenetic) -TRAIT is only seen in one
Epigenetic inheritance
____________is a pattern in which a modification occurs to a nuclear gene or chromosome that alters gene expression, but is not permanent over the course of many generations. Epigenetic inheritance patterns are the result of DNA and chromosomal modifications that occur during oogenesis, spermatogenesis, or early stages of embryogenesis
A typical gene will consist of?
a coding region a promoter a termination code
In an initial cross, a female with the genotype Aa is crossed with a male with the genotype aa. In a reciprocal cross the female's genotype should be______ and the males genotype should be_____
aa Aa
In mice if you delete the Igf2 gene from a female, and then mate her with a normal sized male, what will the phenotype of the progeny be?
all will be normal sized
sex influenced traits
an autosomal trait that is influenced by the presence of male or female sex hormones -autosomal -variable expression due to environment in which they are found (testosterones etc)
What characteristics do mitochondria and chloroplasts share with bacteria?
circular DNA (at least typically) a membrane composed predominately of phospholipids the ability to self-replicate (make more of themselves)
If a reciprocal cross involved a female with the genotype pp and a male with the genotype Pp. Then in the initial cross the female's genotype was Pp___ and the male's genotype was pp____
correct
downregulation and upregulation
does of x-linked genes between males and females, but also relative to autosomes -why downregulate/inactivate AND upregulate single active X in mammals?
What is true of X chromosome inactivation in mammals?
during mitosis both copies of the inactivated chromosome remain compacted one X chromosome becomes highly compacted, inactivating most of the genes on it a somatic cell that is the result of mitosis will retain the inactivation of the barr body in the "mother" cell
Identical twins are separated at birth. 25 years later, the twins are reunited. Even though the twins are genetically identical, there are obvious differences in their physical appearance: Twin 1 is 5'9" and has a fair complexion, Twin 2 is 5'6" and has a darker complexion. As identical twins, they have the identical genotype. What can account for the difference in phenotype?
epigenetic modifications environmental impacts on gene regulation
What is the molecular explanation for maternal effect in mammals?
exposure to the mother's gene products during embryo development influences the resulting offspring's phenotype cells surrounding the developing embryo transmit gene products to the embryo cells surrounding the embryo produce gene products that reflect the mother's genotyp
Non-nuclear DNA is often inherited biparentally, meaning that offspring get DNA from both the male and the female parent.
faLSE
The X chromosome inactivation is a controlled process that occurs after embryogenesis is complete.
false
paternal leakage occurs when the mitochondria of the sperm is lost just before fertilization.
false
Which of the following is true of human X-linked recessive traits
females can carry the trait but will only show the trait if they have two recessive alleles
genomic imprinting must involve a ______________. A particular gene or chromosome must be marked differently during spermatogenesis versus oogenesis. After fertilization takes place, this differential marking affects the expression of particular genes
marking process
What changes in a chromosome will make it inactive?
methylation
If a male inherits an unmethylated gene from his mother and a methylated gene from his father what will happen during gametogenesis?
the methylation of the paternal gene will be erased and then de novo methylation will occur in both genes before gamete formation
A mitochondrion has multiple copies of its DNA, and a typical cell has many mitochondria.
true
At the cellular level, imprinting is an epigenetic process that can be divided into three stages: (1) the establishment of the imprint during gametogenesis, (2) the maintenance of the imprint during embryogenesis and in adult somatic cells, and (3) the erasure and reestablishment of the imprint in the germ cells
true
At the start of meiosis the cell that is going to divide is diploid______. It contains two copies________ of each gene. At the end of meiosis each resulting cell is haploid______ and each contains one copy______ of each gene
true
In germ-line cells the Barr Body is reactivated because two copies of some X linked genes are needed for the successful completion of oogenesis.
true
On the active X chromosome the Tsix is expressed and the Xist is not expressed
true
On the inactive X chromosome (the Barr body) the Xist is expressed and the Tsix is not expressed.
true
The pyrimidine____ cytosine forms a hydrogen_____ bond with the purine______ guanine to help form double stranded DNA
true
