Epigenetics

Question 1

Which does not constitute a major epigenetic mechanism involved in mammalian X inactivation
- association with Xist RNA
- cytosine methylation
-histone methylation
- gene reaarangement

Answer 1

gene rearrangement

Question 2

Which statement is not true about imprinted genes
- imprinting affects a small subset of genes and results in the expression of those genes from only one of the two parental chromosomes
-Nearly all imprinted genes are organized in clusters in the genome
-Imprinting is maintained in the primordial germ cells
-Imprinting occurs in mammals, but no other vertebrates studied so far

Answer 2

Imprinting is maintained in the primordial germ cells

Question 3

Cytosine methylation
-makes genes for silencing
-marks genes for expression
-marks genes for deletion
-marks genes for transcription but not translation

Answer 3

-marks genes for silencing

Question 4

Inherited defects that are not due to alterations in the DNA sequence are referred to as:
- Loss of function
-dominant negative
-recessive
-epigenetic

Answer 4

epigenetic

Question 5

Methylation patterns are erased during germ cell development and then re-established at the zygote stage
-True
-False

Answer 5

true

Question 6

When the allele choice is determined by its parent-of-origin, monoallelic gene expression is referred to as
-imprinting
-gene switching

Answer 6

gene switching

Question 7

Angelman syndrome and Prader-Willi syndrome are imprinting disorders that map to a 2-Mb location at 15q11-13
-True/False

Answer 7

True

Question 8

the relevance of CpG islands is that they tend to be found
-Just upstream gene sequences
-At the 3’ end of genes greater than 1kb in length
-In clusters within introns
-Traversing exonic and intronic sequences

Answer 8

Just upstream of gene sequences

Question 9

A CpG island refers to C lying next to G along a piece of DNA where p probably denotes
- Phosphoester bond
-phosphate bond
-phosphorus bond
-phosphodiester

Answer 9

-Phosphodiester bond

Question 10

sodium bisulphite treatment followed by exposure to high pH converts normal cytosine to
-adenine
-uracil
-thymine
-guanine

Answer 10

uracil

Question 11

X chromosome inactivation in humans is:
- preferential for the paternal X chromosome
- random
-non-random
can be random or non-random depending on the particular gene

Answer 11

is non-random

Question 12

Inherited genes are regualted by impriminting control regions- within these regions there are allele-specific difference in:
-the location of CpG islands
- DNA methylation and histone modification
-DNA methylation
-Histone modification

Answer 12

DNA methylation and histone modification

Question 13

The silenced X chromosome in females is commonly referred to as
- The inactive sex chromosome
- The inactive autosome
-The banded body
- The barr body

Answer 13

The barr body

Question 14

the inactive X chromosome in females is completely silenced
-T.F

Answer 14

False

Question 15

The dinucleotide CG is underrepresented in the human genome because:
- it is highly deleterious in most genomic locations due to methylation
-methylcytosine is read as an thymine during replication, resulting in CA dinucleotide
-methylcytosine is highly susceptible to spontaneous deamination, resulting in the TG dinucleotide
-methyltransferases cannot methylate cytosine’s when a guanine is the next nucleotide

Answer 15

methylcytosine is highly susceptible to spontaneous deamination, resulting in the TG dinucleotide

Question 16

Monoallelic expression mechanism is due to:
- Altered chromatin structure in the gene promoter
-Differential expression of an antisense RNA transcript
Blocking of an enhancer
-All of the above

Answer 16

All of the above

Question 17

When a pregnant female of a particular strain of yellow agouti mice with the agouti viable yellow [Avy] allele was fed a diet rich in folic acid, the mouse give birth to offspring with mostly brown fur indicating:
-an LTR retrotransposon was hypermethylated and moved from one chromosome to another, thereby shutting off expression of the agouti gene
- the retrotransposon promoter region was hypermethylated thereby shutting off expression of the downstream agouti gene
-the retrotransposon promoter region was hypomethylated thereby shutting off expression of the downstream agouti gene
- an LTR retrotransposon was hypermethylated and moved from one chromosome to another thereby turning on expression of the brown fur gene

Answer 17

the retrotransposon promoter region was hypermethylated thereby shutting off expression of the downstream agouti gene

Question 18

As a general rule cytosine DNA methylation marks genes for
- mutation
-activation
-programmed gene rearrangements
-silencing

Answer 18

silencing