Lecture 23 Flashcards

1
Q

4 important processes in DNA replication

A

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

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2
Q

Are there one or many origins of replication in eukaryotes

A

many, because of their size

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3
Q

A bubble of replication is made of

A

two replication forks

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4
Q

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

A

two helixes,two daughter DNA molecules

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5
Q

DNA reads in which direction and synthesizes in which direction

A

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

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6
Q

Fragments are how many nucleotides per piece?

A

100

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7
Q

when the DNA is continuous, it is called the

A

leading strand

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8
Q

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

A

lagging strand (Okazaki fragment)

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9
Q

replication fork

A

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

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10
Q

origin of replication

A

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

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11
Q

Helicases

A

unwind DNA; more they unwind, the tighter they become

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12
Q

Topoisomerases

A

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

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13
Q

Single Strand Binding Proteins

A

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

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14
Q

Primase

A

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

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15
Q

the RNA primer does what for the polymerase?

A

leaves the 3’ end free so it can act accordingly

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16
Q

dATP, dCTP, dGTP, dTTP

A

d = deoxyribose

17
Q

a replication bubble is formed when

A

proteins attach and separate the DNA strands

18
Q

DNA polymerase III

A

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

19
Q

DNA polymerase III reads and elongates in which direction?

A

reads 3’ to 5’, elongates 5’ to 3’

20
Q

DNA polymerase III is activated from

A

primase giving it a short sequence of ribonucleotides

21
Q

DNA polymerase I

A

enzyme that removes and replaces the RNA primer

22
Q

ligase

A

an enzyme that ligates (joins) ends of DNA molecules

23
Q

DNA polymerase has a function of

A

proofreading

24
Q

mismatched nucleotides evade proofreading or occur after DNA replication because of

A

exposure of cells to insults such as carcinogens and UV light

25
mismatched nucleotide problem is fixed by
enzymes in the cell that detect and repair the DNA (130 of them)
26
Nucleosomes contain
H2A, H2B, H3, H4
27
the histone H1 attaches
to the nucleosome
28
Histones can be modified either through
methylation or acethylation
29
methylation
condensation of DNA, prevents transcription of genes
30
acethylation
promotes de condensation of DNA and allow transcription of genes
31
Levels of chromatin packing
DNA, nucleosomes, chromatin fiber, looped domains, metaphase chromosome
32
chromatin
complex of DNA and protein that make up eukaryotic chromosome
33
euchromatin
less condensed form available for transcription
34
heterochromatin
highly compacted, generally, not transcribed