DNA Structure

Question 1

Chargaff’s First Rule

Answer 1

A-T, G-C

Question 2

Chargaff’s Second Rule

Answer 2

Composition of DNA varies from one species to another but not within an organism

Question 3

What’s on the 5’ end?

Answer 3

Phosphate group

Question 4

What’s on the 3’ end?

Answer 4

Hydroxyl group

Question 5

B-DNA

Answer 5

Hydrophillic backbone of each strand is on the outside. Ten base pairs per turn.

Question 6

Z-DNA

Answer 6

Rare left-handed double helix occuring in G-C rich regions.

Question 7

A-DNA

Answer 7

produced by dehydration of B form. 11 base pairs per turn. Conformation found with DNA-RNA hybrids or RNA-RNA double stranded regions.

Question 8

Disruption of non-covalent interactions which hold the DNA duplex together.

Answer 8

Denaturation

Question 9

What can cause DNA denaturation?

Answer 9

Heat, pH extremes, urea, and other denaturation agents.

Question 10

Hyperchromic effect in DNA

Answer 10

Denatured DNA become less viscous and absorb (more) ultraviolet light

Question 11

Melting Temperature

Answer 11

50% of double-stranded DNA, 50% single-stranded

Question 12

Which are weaker, A-T hydrogen bonds or G-C?

Answer 12

A-T

Question 13

What is the single circular chromosome of bacteria called?

Answer 13

nucleoid

Question 14

What are the additional, small circular DNA that bacteria have called?

Answer 14

Plasmids

Question 15

Chromatin

Answer 15

DNA/RNA and proteins (incl. histones)

Question 16

What sorts of amino acid residues do histones have?

Answer 16

Basic / positively charged. (DNA is negative)

Question 17

Nucleosome

Answer 17

Structural unit for chromatin packaging. DNA wound around a histone core.

Question 18

What are the components of a histone core?

Answer 18

Two copies of: H2A, H2B, H3, H4

Question 19

What, alongside linker DNA, is found between nucleosomes

Answer 19

Histone H1

Question 20

Nucleosomes make up…

Answer 20

Chromatin

Question 21

Euchromatin

Answer 21

Loosely packaged and transcriptionally active

Question 22

Heterochromatin

Answer 22

Tightly packaged and transcriptionally inactive

Question 23

Positive Supercoiling

Answer 23

Winding in the same direction of the double helix turns

Question 24

Negative Supercoiling

Answer 24

Winding in the opposite direction of the double helix turns

Question 25

What maintains underwinding and relaxes supercoiling effects?

Answer 25

Topoisomerases

Question 26

Group of antibiotics targeting topoisomerase

Answer 26

Quinolones (specifically, ciprofloxacin)

Question 27

Chemotherapy drug blocking topoisomerase

Answer 27

Doxorubicin

Question 28

Specialized repeat DNA sequence with specialized proteins, found at the end of eukaryotic chromosomes

Answer 28

Telomere

Question 29

Ori site

Answer 29

Origin of replication; nucleotide squence at which DNA synthesis begins

Question 30

What is the chromosomal complement of a cell, individual or species called?

Answer 30

Karyotype

Question 31

Two functions of DNA methylation

Answer 31

1) inhibiting the binding of transacting factors (usually promoters but can also block repressive factors) 2) recognition motif for binding of specific factors

Question 32

Enzyme that catalyze DNA methylation

Answer 32

DNA Methyltransferases (DNMTs)

Question 33

What serves as the donor for DNA methylation?

Answer 33

S-adenosyl Methionine

Question 34

Removal of DNA methylation

Answer 34

Ten-Eleven Translocation (TET) enzymes followed by base-excision repair using Thymine-DNA Glycosylase (TDG)

Question 35

Possible modifications of histones

Answer 35

acetylation, phosphorylation, methylation, ADP-ribosylation, glycosylation, ubiquination, amino-terminal modifications.

Question 36

Histone Code

Answer 36

Histone covalent modifications (collectively)

Question 37

Catalyze the transfer of an acetyl group from acetyl-CoA to epsilon-amino group of histone lysine residue

Answer 37

Histone Acetyltransferases (HATs)

Question 38

Responsible for removing acetyl groups from histones.

Answer 38

Histone Deacetylases (HDACs)