quiz 12 Flashcards

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1
Q

DNA is a polymer made of

A

nucleotides

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2
Q

In what order do the following processes occur during DNA synthesis?

Topoisomerase (Gyrase) relieves the stress created by the unraveling of the DNA double helix

Primase synthesizes the first primer

DNA polymerase begins synthesis of the leading strand

Primase synthesizes primers for lagging strand synthesis

DNA helicase denatures double stranded DNA

DNA polymerase I removes the primers

Once replication has begun DNA helicase continues to open the replication bubble

Ligase connects all the newly replicated strands of DNA

A

DNA helicase denatures double stranded DNA

Topoisomerase (Gyrase) relieves the stress created by the unraveling of the DNA double helix

DNA polymerase begins synthesis of the leading strand

Primase synthesizes the first primer

Once replication has begun DNA helicase continues to open the replication bubble

Primase synthesizes primers for lagging strand synthesis

DNA polymerase I removes the primers

Ligase connects all the newly replicated strands of DNA

2
4
3
6
1
7
5
8

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3
Q

Why is an RNA primer necessary to initiate DNA synthesis?

A

DNA polymerase requires a 3’ hydroxyl to add a new nucleotide

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4
Q

Denatures double stranded DNA

A

helicase

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5
Q

Removes primers

A

DNA polymerase I

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6
Q

Synthesizes a primer made of RNA

A

Primase

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7
Q

Connects fragments of DNA produced during DNA synthesis

A

Ligase

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8
Q

Relieves stress created by the denaturation double stranded DNA

A

Gyrase

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9
Q

What does DNA polymerase require?

A

A single stranded DNA to act as a template
A free 3’ hydroxyl
Unbound nucleotides

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10
Q

DNA synthesis

A

Each of the two existing strands act as a template to produce new double strands

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11
Q

What enzyme best synthesizes a new strand of DNA?

A

DNA polymerase

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12
Q

How can DNA polymerase be the source of mutation?

A

It may incorrectly match nucleotides

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13
Q

Why is ionizing radiation a mutagen?

A

It can break double stranded DNA

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14
Q

How do oxygen radicals create mutagens?

A

They attach to cytosine to make a nucleotide that pairs with adenine rather than guanine

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15
Q

Why is ultraviolet light a mutagen?

A

It can fuse two adjacent thymine nucleotides and change the topology of the DNA molecule

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16
Q

What is the exonuclease activity of DNA polymerase

A

Its ability to remove nucleotides and correct base pairing mistakes

17
Q

What is the outcome of a genetic mutation?

A

A loss of protein function leading to a recessive phenotype
A gain of protein function leading to a new dominant phenotype
Or nothing at all

18
Q

What is the role of an existing double stranded helical DNA in the synthesis of new strands?

A

Serves as a template for its own replication

19
Q

What direction does DNA polymerase synthesize a new strand?

A

5 to 3

20
Q

What direction does DNA polymerase read the strand?

A

3 to 5

21
Q

What does DNA Polymerase I do?

A

Removes RNA primers and replaces them with DNA by way of exonuclease activity

22
Q

What is the difference between lagging and leading strand synthesis?

A

Leading - continous 5 to 3 uninterupted synthesis
Lagging - upstream of leading - production of small fragments of DNA upstream of the leading strand to prevent degredation of single-stranded DNA

23
Q

Why is lagging strand synthesis necessary?

A

Without it a large portion of DNA would go unreplicated/unsynthesized

24
Q

What is genetic mutation?

A

A change in DNA nucleotide sequences
Mutations can be good bad, or neutral

25
Q

What sources of DNA mutation did we cover?

A

DNA polymerase may mistmatch base pairs during replication - Single Nucleotide Polymorphism
Mutagens

26
Q

How does a DNA polymerase usually repair a mismatched base pair?

A

Exonuclease

27
Q

What is the difference between polymerase and exonuclease?

A

Exo = removal, Poly = adding

28
Q

What is a mutagen?

A

Environmental phenomena that alters or changes DNA

29
Q

How does ultra-violet damage DNA?

A

uses adjacent thymines to create thymine dimers - changes shape of DNA molecule

30
Q

What is the general repair mechanism that fixes damaged or mismatched base pairs?

A

Excision repair

31
Q

What is the process of excision repair?

A

Nucleases make cuts on both sides of mutation, stretch of DNA w/ mutated nucleotides is removed, DNA polymerase fills in the nucleotides that were removed