Chapter 19 Epigenetics

Question 1

What does DNMT1. DNMT3a AND DNMT3b do as a group?

Answer 1

act as DNA methyltransferases, adding methyl groups to cytosines adjacent to guanines

Question 2

What does DNMT1 do? Wat dies DNMT3a and DNMT3b do?

Answer 2

DNMT1- maintain patterns DNMT3a and DNMT3b- establish original patterns

Question 3

What does miRNA do?

Answer 3

Promotes mRNA degredation

Question 4

How does a heart cell access specific genes, while a neuron cell accesses specific genes?

Answer 4

Different regions of DNA with histones are condensed, leading to no expression while others are relaxed, leading to expression and being transcriptionally active

Question 5

What are two major mechanisms of epigenetic inheritance?

Answer 5

Modifications to DNA and histones

Question 6

How can modifications help DNA?

Answer 6

help solve packaging problem allowing restriction or access to genes

Question 7

Enzymatic modification of _______ at _____ nucleotides can _______ transcription

Answer 7

cytosines, CpG, decrease

Question 8

How are methyl groups involved in transcriptional repression?

Answer 8

interferes with the binding of proteins to DNA

Question 9

Explain how De Novo mutations with DNA methylation involving DNMT1, 3a, and 3b occur

Answer 9

DNMT1, maintenance DNA methylation fully restores the methylated state. First, during mitosis dmt3a and b will methylate the daughter strand and not the parent strand, after mitosis, DNMT1 will maintain the state of the daughter strand and its methyl groups.

Question 10

DNA methylation _________ expression of agouti coat gene, it is sensitive to environmental exposure, specifically _________

Answer 10

suppresses, diet

Question 11

Can inherited behavior be caused by epigenetic changes? give one example

Answer 11

Yes, rat mothers with high maternal nurturing (Hi-LG) produced offspring who exhibited the same behavior towards their offspring. Pups from Hi-LG mothers also had elevated glucocorticoid receptor gene expression with low DNA methylation at the promoter.

Question 12

What does imprinting result in? What is expressed from the maternal and paternal chromosomes? What does DNA methylation at the imprinting control region allow?

Answer 12

-monoallelic gene expression (one expressed one repressed)
-maternal- H19, paternal- IGF2
-blocks binding of transcription factor (CTCF) and allows enhancer to drive expression of IGF2

Question 13

What is Bi sulfite sequencing? What does it do?

Answer 13

• technique to measure DNA methylation
  -converts unmethylated cytosine to uracil, which is amplified as thymine during PCR, the percentage of methylated cytosines can be calculated after

Question 14

What does SWI/SNF do? (Histone modifications)

Answer 14

allow chromatin access for easier expression by repositioning, ejecting, or evicting nucleosome dimers. They also exchange histones and assemble nucleosomes.

Question 15

What are some post-translational modifications of histones?

Answer 15

• occur at amno acids of histone n-terminal tails
  -writer- HATS
  -Eraser-HDAC
  -writer- KMT (histone methyltransferases, adds methyl groups to lysines)
  -eraser- KDM (removes methyl groups)

Question 16

Histone code hypothesis

Answer 16

distinct histone modifications on one or more tails act sequentially/ combination to be read by other protein to bring other events

Question 17

How does position effect variegation occur? (histone modification)

Answer 17

gene juxtaposed next to repressive heterochromatin, an inversion occurs

Question 18

How are miRNA’s epigenetic regulators?

Answer 18

influence expression of target gene without altering sequence

Question 19

How can miRNA influence genes?

Answer 19

miRNA genes transcribed and formed to RISC-RNA, can cleave mRNA or inhibit translation

Question 20

lncRNA are classified by _______ but function is not determined by _________

Answer 20

location, location

Question 21

Describe te 4 types of lncRNA (IBAS)

Answer 21

Intergenic - lncRNA in between already spliced exons on the coding strand, runs in 3 to 5
bidirectional - exon on coding strand moving 3 to 5, incrna moving 3 to 5 on noncoding
antisense - incrna on non coding moving 3-5, overlapping nonspliced sequence on coding strand moving in 3 to 5
sense-overlapping - exons and incrna moving 3 to 5 on coding strand

Question 22

What contributes to XCl? (x chromosome inactivation)

Answer 22

non coding rna, sitone modifications, dna methylation