Ch. 21 I'm Exhusted.

Question 1

EpiGENESIS

Answer 1

How embryo develops

Question 2

Epigenetics is alterations to _______ that affect ____ and are ________ but are NOT _______________________________.

Answer 2

Epigenetics is alterations to DNA and Chromatin structure that affect traits and are passed on to other cells or generations but are NOT caused by changes in DNA base sequences.

Question 3

Changes in chromatin structure alter

Answer 3

gene expression

Question 4

Name 3 molecular mechanisms that alter chromatin structure

Answer 4

1. Changes in patterns of DNA methylation
2. Chemical modification of histone proteins
3. RNA molecules that affect chromatin structure and gene expression

Question 5

DNA methylation

Answer 5

Repression of transcription
CpG dinucleotides
Prevents transcription factors from binding
Located near or in promoters
Attracts histone deacetylases or methyl transferases

Question 6

How is methylation maintained

Answer 6

Template strand methyl groups attract methyltransferases, which add methyl groups to unmethylated strands
This is how epigenetic changes are retained and replicated through the process of chromosome replication

Question 7

How are Queen Bees created?

Answer 7

Royal Jelly: Inhibiting Dnmt3, causing demethylation

Question 8

Histone Modifications

Answer 8

Phosphates, methyl (effect varies), acetyl (more transcription when added), ubiquitin

Question 9

Histone modifications which don’t involved base sequence that are associated with level of transcription are called

Answer 9

Epigenetic markers

Question 10

Histone modifications are added and removed by _____, a group of proteins that (repress/active) transcription by modifying histones.

Answer 10

polycomb group (PcG)

Repress transcription

Question 11

One histone may affect whether addition marks occur nearby and how they function. This is called

Answer 11

Crosstalk

Question 12

Paramutation

Answer 12

interaction between two alleles that leads to heritable change in expression of one allele

Question 13

2 important features of paramutation

Answer 13

1. newly established expression pattern of converted allele is transmitted to future generation, even though allele is no longer present
2. Altered allele now able to convert other alleles to the new phenotype

Question 14

Paramutation in Mice: Why do some kit(t) kit(t) mice have white feet and tails

Answer 14

miRNAs that degrade the Kit in mRNA, transmitted through gametes

Question 15

Paramutation in Corn: How does B’ convert B-I allele to B’*

Answer 15

siRNAs encoded by tandem repeats

Modify chromatin structure by directing DNA methylation

Question 16

Describe X inactivation

Answer 16

Xist gene transcribed to lncRNA, which coats Xi but not Xa. The Xist RNA recruits PCR2 which produces histone modifications on Xi.

Question 17

What inhibits transcription of Xist on ACTIVE chromosome?

Answer 17

Tsix

Question 18

What stimulates transcription of Xist on INACTIVE chromosome?

Answer 18

Jpx

Question 19

What sustains Tsix expression on active X, which inhibits Xist and maintains transcription of genes on active X chromosome.

Answer 19

Xite

Question 20

What is it called when sex of parent that contributed the allele influences how allele is expressed, and why does this happen?

Answer 20

Genomic Imprinting

Due to different degrees of methylation of the alleles inherited from the two parents

Question 21

Genomic Imprinting: Mice example

Answer 21

When mutant from father, expressed, but not if from mother

Question 22

The overall pattern of chromatin modifications possessed by each individual organism

Answer 22

Epigenome

Question 23

How are histone modifications detected?

Answer 23

ChIP- break chromatin into fragments, applies antibody specific to particular histone modification. (Rest explained in pervious chapters)

Question 24

Detecting DNA methylation: 2 methods

Answer 24

1. Restriction endonucleases

2. Bisulfate sequencing

Question 25

Bisulfate sequencing

Answer 25

Converts unmethylated cytosine to uracil. (C –> U)
Uracil detected as thymine
5mC is detected as cytosine