Lecture 23

Question 1

4 important processes in DNA replication

Answer 1

Unwinding of strands, initiation of replication, elongation of DNA strands being replicated, termination of replication

Question 2

Are there one or many origins of replication in eukaryotes

Answer 2

many, because of their size

Question 3

A bubble of replication is made of

Answer 3

two replication forks

Question 4

in DNA replication, you start with one helix and end with

Answer 4

two helixes,two daughter DNA molecules

Question 5

DNA reads in which direction and synthesizes in which direction

Answer 5

it reads in the 3’ to 5’, but synthesizes in the 5’ to 3’

Question 6

Fragments are how many nucleotides per piece?

Answer 6

100

Question 7

when the DNA is continuous, it is called the

Answer 7

leading strand

Question 8

when the DNA is in bits and pieces, it is called the

Answer 8

lagging strand (Okazaki fragment)

Question 9

replication fork

Answer 9

y-shaped region of replicating DNA where parental DNA strands are unwound, and DNA replication takes place

Question 10

origin of replication

Answer 10

part in the fork (region of DNA) that has specific sequence of nucleotides and where DNA replication begins

Question 11

Helicases

Answer 11

unwind DNA; more they unwind, the tighter they become

Question 12

Topoisomerases

Answer 12

cut DNA strands and rejoin in loops so that they become less tight

Question 13

Single Strand Binding Proteins

Answer 13

stabilizers that bind to the unpaired DNA strands during replication, holding them while they serve as templates

Question 14

Primase

Answer 14

RNA polymerase + RNA nucleotides that make the primer using parental DNA as a template

Question 15

the RNA primer does what for the polymerase?

Answer 15

leaves the 3’ end free so it can act accordingly

Question 16

dATP, dCTP, dGTP, dTTP

Answer 16

d = deoxyribose

Question 17

a replication bubble is formed when

Answer 17

proteins attach and separate the DNA strands

Question 18

DNA polymerase III

Answer 18

complex of enzymes at the end of polymerase which makes the new strand, copying it from the old strand

Question 19

DNA polymerase III reads and elongates in which direction?

Answer 19

reads 3’ to 5’, elongates 5’ to 3’

Question 20

DNA polymerase III is activated from

Answer 20

primase giving it a short sequence of ribonucleotides

Question 21

DNA polymerase I

Answer 21

enzyme that removes and replaces the RNA primer

Question 22

ligase

Answer 22

an enzyme that ligates (joins) ends of DNA molecules

Question 23

DNA polymerase has a function of

Answer 23

proofreading

Question 24

mismatched nucleotides evade proofreading or occur after DNA replication because of

Answer 24

exposure of cells to insults such as carcinogens and UV light

Question 25

mismatched nucleotide problem is fixed by

Answer 25

enzymes in the cell that detect and repair the DNA (130 of them)

Question 26

Nucleosomes contain

Answer 26

H2A, H2B, H3, H4

Question 27

the histone H1 attaches

Answer 27

to the nucleosome

Question 28

Histones can be modified either through

Answer 28

methylation or acethylation

Question 29

methylation

Answer 29

condensation of DNA, prevents transcription of genes

Question 30

acethylation

Answer 30

promotes de condensation of DNA and allow transcription of genes

Question 31

Levels of chromatin packing

Answer 31

DNA, nucleosomes, chromatin fiber, looped domains, metaphase chromosome

Question 32

chromatin

Answer 32

complex of DNA and protein that make up eukaryotic chromosome

Question 33

euchromatin

Answer 33

less condensed form available for transcription

Question 34

heterochromatin

Answer 34

highly compacted, generally, not transcribed