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Biology gr12 > DNA replication > Flashcards

DNA replication Flashcards

1
Q

What does DNA replication do and when does it happen?

A

Produces two identical copies of the
chromosome during S phase of
interphase.

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2
Q

DNA replication is catalyzed by many..

A

enzymes

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3
Q

The structure of DNA allows it to be easily…….

A

replicated

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4
Q

_________ between base pairs can be broken (unzipped) and each strand acts as a ________ for adding new nucleotides.

A

H-bonds, template

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5
Q

What are the three steps of replicating DNA?

A

Separating the DNA strands

Building complementary strands

Linking of Nitrogenous Bases

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6
Q

What happens in the first step of DNA replication, separating the DNA strand?

A

Enzymes and other proteins work
together to unwind and stabilize the
double helix

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7
Q

What are the players/enzymes in step one (separating the DNA strand) in DNA replication?

A

DNA helicase

DNA gyrase

SSBs

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8
Q

What does DNA helicase do?

A

Recognizes specific nucleotide
sequence (origin of replication)

Unwinds double helix by breaking H
bonds between complementary base
pairs

Opens up replication bubble

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9
Q

What does DNA Gyrase do?

A

Relieves the tension produced by
the unwinding of DNA

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10
Q

What does SSBs (Single-stranded Binding Proteins) do?

A

Keep separated DNA strands apart
by blocking hydrogen bonding

Keep the templates (single DNA
strands) straight

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11
Q

What is the replication fork?

A

The junction where the DNA strands
are still joined

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12
Q

What happens during the second step of DNA replication (Building complementary strands)?

A

Replication begins in two directions
from the origin(s) as a region of DNA is unwound

Replication proceeds towards the
replication fork on one strand, and away from the fork on the other strand.

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13
Q

Because there may be
more than one origin of
replication in eukaryotes,
more than one ___________ _____ may exist.

A

replication fork

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14
Q

What are the players in the second step of DNA replication (Building complementary strands)?

A

DNA polymerase

primase

DNA ligase

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15
Q

What does DNA polymerase III do?

A

Takes free nucleotides found
within the cell and adds them in the
5’ to 3’ direction

The parent strand is used as a
template

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16
Q

What is the leading strand what does it do?

A

The daughter strand that grows
continuously towards the replication
fork as the double helix unwinds

Occurs quickly

Requires a single RNA primer

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17
Q

What is the lagging strand in DNA replication?

A

Built in short segments (in the 5’ to 3’ direction) away from the replication fork

Requires many RNA primers

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18
Q

Why is the 3’ to 5’ strand a problem for DNA polymerase?

(More details for lagging strand.)

A

The 3’ to 5’ parent strand is a problem for DNA polymerase since it must synthesize in the 5’ to 3’ direction.

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19
Q

What does Primase do in the second step of DNA replication (Building complementary strands)?

A

Builds RNA primers (used to initiate DNA replication)

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20
Q

What are Okazaki Fragments?

A

Short fragments of DNA built by
DNA polymerase off of the RNA
primers

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21
Q

What does DNA Polymerase I do in step two of DNA replication?

A

Removes the RNA primers once they
have been used and replaces them with the appropriate DNA sequence

22
Q

What does DNA ligase do in step two of DNA replication?

A

Joins the Okazaki fragments into one
strand by the creation of phosphodiester bonds

23
Q

What happens in step 3 of DNA replication (Linking Nitrogenous Bases) ?

A

Nitrogen bases of nucleotides of
opposite strands (parent and daughter)
form new H bonds

Once bonds are formed, DNA twists
automatically into a double helix

24
Q

Why is DNA polymerase consider the quality controller enzyme thingy

A

DNA polymerase acts as a
proof-reader by checking the newly
synthesized strand for any incorrectly inserted bases

25
Q

A human cell can copy all of its DNA in a couple of hours
with an error rate of __ ____ _________ nucleotide pairs.

A

1 per billion

26
Q

The most common type of error is mispairing, such that a __
is paired with __.

A

T is paired with G

27
Q

Another error is caused by _______ _________ during
replication.

A

strand slippage

28
Q

What does strand slippage result in?

A

This can result in addition or deletion of nucleotides in the newly synthesized strand.

29
Q

Most polymerases have the ability to ___________.

A

proofread.

30
Q

When an incorrect nucleotide is placed on the newly
synthesized strand, replication is stalled as the __’ end is in
the wrong position for the next to attach.

A

3’

31
Q

The two strands of DNA are..

A

Antiparallel

32
Q

What holds the nucleotides together?

A

H-bonds

33
Q

How many bonds between A and T? C and G?

A

2 h-bonds for A and T. 3 h-bonds for C and G

34
Q

What is Exonuclease enzyme?

A

It is the enzyme that removes nucleotides from a strand, starting at one end of the strand. If a mistake is found, it immediately cuts out the mistake

35
Q

What are Okazaki Fragments?

A

Short fragments of DNA built by
DNA polymerase off of the RNA
primers

36
Q

DNA polymerase acts as a
proof-reader by checking the newly
synthesized strand for any incorrectly inserted bases

If a mistake is found, act as an
____________ – & cut out the mistake

A

exonuclease

37
Q

What is another mechanism that corrects errors in both eukaryotes and prokaryotes that were not fixed
during proofreading?

A

Mismatch repair

38
Q

What are Telomeres?

A

Telomeres are long, non-coding, highly-repetitive sequences of DNA at the ends of eukaryotic chromosomes.

39
Q

Video for DNA replication

A

https://www.youtube.com/watch?v=3jslVQDGkLU

40
Q

Why are telomeres necessary?

A

They are necessary as DNA synthesis can only occur in the
5’-3’ direction.

41
Q

The length of the telomeres
is closely linked to the
lifespan of an __________.

A

organism

42
Q

Telomerase is enzyme that
can synthesize _________ _________ that have been lost.

A

telomeric regions

43
Q

Telomerase activity high
during __________ when
tissues are growing rapidly.
Telomerase activity slows in
_______ _______ as
people age.

A

childhood, somatic cells (body)

44
Q

If we could maintain high telomerase activity, we would
___ _____ ________.

A

age much slower.

45
Q

High telomerase activity is what allows for ________ _______ ____ _______. High telomerase activity allows for the tumor cells to continue to ________ as important genes would not be lost.

A

cancerous tumors to grow, replicate

46
Q

What do telomeres prevent?

A

They prevent the loss of important DNA during replication, as the copying process can’t fully replicate the very ends of chromosomes.

47
Q

Over time, telomeres shorten, which is linked to …..

A

aging and cell death.

48
Q

How does DNA replicate?

A

Back to interphase.

49
Q

In mitosis the ______ DNA molecule is replicated, but for RNA synthesis, only ________ of the DNA are replicated.

A

entire, portions

50
Q

In DNA replication, it is controlled by the enzyme called

A

DNA polymerase

Biology gr12 (23 decks)

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