epigenetics

Question 1

epigentics is the study of ____ that are….

Answer 1

study of heritable changes in gene expression that are NOT due to changes in DNA sequence

Question 2

comparison b/w genetic & epigenetic phenomena

Answer 2

mendelian genetics:
phenotype = mutant
genotype = mutant

epigenetics:
phenotype = mutant
genotype = wildtype

Question 3

3 common epigenetic mechanisms

Answer 3

1- DNA methylation (a subset of cytosine residues could be modified by methylation)

2- histone modification/histone variants

3- regulatory non-coding RNAs (ncRNA or RNAi)

Question 4

gene silencing

Answer 4

during early embryogenesis there is a random inactivation of one X chromosome in females so as to prevent the overexpression of X chromosomal genes

consequence –> one allele is expressed in some areas of the body & the other allele is expressed in other areas

Question 5

typically, the sites of DNA methylation are on the ___ site of…

Answer 5

5C site of cytosine in CpG dinucleotides

Question 6

why is epigenetics important? 3 kinds of frequent epigenetic changes have been identified in tumors

Answer 6

1- genome-wide hypomethylation
2-tumor-suppressor genes can be inactivated by dense hypermethylation of their upstream regulatory sequences
3- loss of parental imprinting

Question 7

2 distinct types/patterns of methylation

Answer 7

1- maintenace - (methyltransferases)
2- De novo - (methyltransferases, highly expressed at embryo implantations when waves of de novo methylation are occurring in the genome)

Question 8

the knockout of any methyltransferase genes is ___ during early development or shortly thereafter

Answer 8

lethal

Question 9

imprinting is the epigenetic process where…

Answer 9

one of the parental alleles is silenced (maternal or paternal)

Question 10

methylation can block ___ of a gene, similar to a mutation in that gene

Answer 10

transcription (expression)

Question 11

detection of methylated cytosine in DNA - once DNA has been treated (bisulfite conversion occurs), then it can be distinguished by ___, ___, or ___

Answer 11

PCR
sequencing
methylation specific enzymes

Question 12

while DNA methylation is widespread in plants, fungi, and animals, it has been curiously lost/low in some of the most well studied genetic organisms including ___ and ____

Answer 12

yeast & C. elegans

Question 13

some of the most methylated sequences found within genomes are ____

Answer 13

transposable elements

Question 14

histone modifications change ___ structure affecting ___ of DNA

Answer 14

chromatin
accessibility

Question 15

2 mechanisms of histone modification

Answer 15

acetylation
methylation

Question 16

euchromatin are ___ compact and ___ transcribed

Answer 16

less
actively

Question 17

heterochromatin are ___ compact and ___

Answer 17

more
transcriptionally inactive

Question 18

heterochromatic DNA is often ____, while histones are ____ and ___ on residues associated with transcriptional repression

Answer 18

methylated
hypoacetylated & methylatd

Question 19

non-coding RNAs are proposed to control ___ via sequence-specific interactions with ___ regions

___RNAs and ___RNAs bind and & inactivate transcription

Answer 19

gene expression
regulatory

microRNAs & short interfering RNAs

Question 20

small RNA(sRNA) appear to cause/direct ___ of specific genes

Answer 20

methylation

Question 21

how many different microRNA genes are there?

Answer 21

LOTS, it is hard to find accurate numbers, but likely thousands

single miRNAs can potentially target >100 diff mRNAs so each can have huge influence on transcription

Question 22

can multiple epigenetic mechanisms interact?

Answer 22

yes they all interact together
- histones are methylated
- heterochromatin is activated by RNAi