3.3 DNA Organization within Chromosomes Part 2

Question 1

What is chromatin remodeling?

Answer 1

chromatin is temporarily allowed to relax its compact structure and allow certain parts of the DNA to be exposed to protein binding partners

Question 2

What did improved resolution in X-ray diffraction studies show about chromatin?

Answer 2

able to show the nucleosome core particle at an atomic level

Question 3

What was the team led by Timothy Richmond able to show?

Answer 3

unstructured histone tails were not embedded into the compact DNA-protein structure of nucleosomes

Question 4

What is acetylation of histones?

Answer 4

changing the net charge of histones from positive to neutral through enzyme acetyltransferase

Question 5

What is the most well studied modification of histones?

Answer 5

acetylation

Question 6

What is a result of acetylation of histones?

Answer 6

electrostatic interation of DNA-histone is released causing condensed histone bundles to loosen so DNA becomes exposed

Question 7

What is present in DNA regions of high gene activity?

Answer 7

high level of acetylation

Question 8

What is present in DNA regions of low gene activity?

Answer 8

low acetylation

Question 9

What are the three important modifications that can be done to histones?

Answer 9

acetylation
methylation
phosphorylation

Question 10

What is phosphorylation of histones?

Answer 10

transfer of a phosphate group onto serine or histidine causing a net negative charge on histones - reduces interaction between DNA and histones

Question 11

What is methylation of histones?

Answer 11

addition of methyl groups to lysine or arginine to histones causing a a negative charge and less interaction between DNA and histones

Question 12

What is a result of methylation of cytosine?

Answer 12

gene activity is decreased