Epigenetics

Question 1

Definition of epigenetics?

Answer 1

Change in gene function, without changes to the DNA base sequence

Question 2

What is the epigenome?

Answer 2

All of the chemical modifications to all histone proteins and DNA (except base changes) in an organism

Question 3

How can histone proteins be chemically modified?

Answer 3

Through the addition of acetyl groups

Question 4

How can DNA be chemically modified?

Answer 4

Through the addition of methyl groups without changing the base sequence

Question 5

What are some changes in the environment that could lead to changes in the epigenome?

Answer 5

Smoking, exercise, diet

Question 6

What does the chemical modification of histones and DNA control?

Answer 6

how tightly the DNA is wound around them as the intermolecular forces between the histones and the DNA changes

Question 7

What happens to the genes if DNA is more tightly wound?

Answer 7

the genes on that section of DNA are switched off

Question 8

What happens with the gene and promoter regions when DNA is more tightly wound?

Answer 8

Gene and promoter regions are more hidden from transcription factors and RNA polymerase

Question 9

Is histone modification reversible or irreversible?

Answer 9

reversible

Question 10

What is an an acetyl groups?

Answer 10

COCH3

Question 11

Acetylation of histones involves what?

Answer 11

Acetyl groups are added to lysine amino acids on histone proteins so DNA wraps less tightly around the histones
RNA polymerase and transcription factors can bind more easily- gene expression is switched on

Question 12

Acetylation of histones- DNA?

Answer 12

Wraps less tightly around the histones

Question 13

Acetylation of DNA- RNA polymerase and transcription factors?

Answer 13

Can bind more easily

Question 14

Acetylation of histones- gene expression?

Answer 14

Switched on

Question 15

What type of R group does lysine have?

Answer 15

A positively charged R group which forms ionic bonds with the negatively charged phosphate backbone of DNA

Question 16

What does adding acetyl groups to lysine do to the positive ion?

Answer 16

Removes the positive ion-> therefore removing a bond between the histone protein and DNA

Question 17

What does the removal of acetyl groups do to transcription?

Answer 17

Inhibits transcription

Question 18

Where are methyl groups added?

Answer 18

To a carbon molecule on cytosine bases within sequences that contain multiple cytosine and guanine bases

Question 19

Does methylation suppress or express the transcription of the affected gene?

Answer 19

Suppress
Methylated bases attract proteins that bind to the DNA and inhibit transcription

Question 20

What is epistasis?

Answer 20

When the expression of one gene is affected by another gene at a different locus
One gene can mask/modify the expression of another, altering the expected phenotypic ratios

Question 21

Recessive epistasis?

Answer 21

Two copies of the epistatic allele are needed to mask the other gene

Question 22

Dominant epistasis?

Answer 22

Only one copy of the epistatic allele is needed to mask the other gene

Question 23

Ratios for epistasis?

Answer 23

9:4:3

Question 24

Dominant epistasis?

Answer 24

The epistatic gene masks the effect of another gene when at least one dominant allele is present