Lecture 10

Question 1

Difference between a nucleotide and nucleoside?

Answer 1

Nucleotide contains one to three phosphate groups, a base, and a ribose or deoxyribose. Nucleoside only contains a base and a ribose or deoxyribose.

Question 2

All natural DNA contains _____ at the 5’ end and ____ at the 3’ end

Answer 2

A phosphate group; a hydroxyl group

Question 3

Why are DNA molecules negatively charged?

Answer 3

Phosphate groups are found on the outside of the double helix

Question 4

What contributes to making a DNA molecule more stable?

Answer 4

More G+C content increases thermodynamic stability. If two DNA molecules have the same G+C content, the longer molecule is more stable

Question 5

When are chromosomes most densely packed?

Answer 5

During metaphase in mitosis

Question 6

Telomeres consist of repeats of what nucleotides?

Answer 6

Hexameric TTAGGG repeats

Question 7

What does acetylation of a histone do to DNA packing?

Answer 7

It causes the DNA to relax, forming the euchromatin form

Question 8

What does methylation of a histone do to DNA packing?

Answer 8

It causes the DNA to contract into the heterochromatin form

Question 9

Which enzymes are used for acetylation and deacetylation of a histone?

Answer 9

Histone acetyltransferases cause acetylation, while Histone deacetylases cause deacetylation

Question 10

Which enzymes are used for methylation and demethylation of a histone?

Answer 10

Histone methyl transferases

Question 11

What three mechanisms regulate assembly and state of chromatin?

Answer 11

Chromatin modifiers (acetylation, methylation, etc. of histone tails), ATP dependent chromatin modifiers (remodel chromatin by moving/exchanging nucleosomes in relation to DNA), & recruitment of proteins/remodelers to modified histones