DNA Flashcards

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1
Q

How is DMA packaged in chromosomes?

A

Wrapped around histones and then wound up tightly to form solenoids. The sole lids are then cooled many times.

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2
Q

What is a gene?

A

Short section of DNA found on a chromosome that codes for the production of a protein that controls a characteristic

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3
Q

What are the 3 stages in DNA replication?

A

Initiation, Elongation and termination

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4
Q

In what direction does DNA polymerase read?

A

From the 3’ to 5’ only

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5
Q

What is the human genome?

A

The entire DNA sequence for humans (24 chromosomes)

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6
Q

What is the difference between a nucleoside and a nucleotide?

A

A NUCLEOSIDE has no phosphate group attached.

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7
Q

What is the important of nucleosides?

A

They can be moved into and around cells easily before being phosphorylated to become a nucleotide

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8
Q

What does DNA and RNA stand for?

A
DNA = deoxyribonucleic acid 
RNA = Ribonucleic acid
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9
Q

What are the 2 purine bases?

A

Adenine and Guanine

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10
Q

What are the 3 pyrimidine bases?

A

Thymine and Cytosine and uracil

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11
Q

What is the difference between purines and pyrimidines?

A

Purines are bigger as they have 2 loops

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12
Q

What bonds join the sugar phosphate backbone?

A

Phosphodiester bonds

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13
Q

What enzyme unwinds the DNA strands during replication?

A

DNA Helicase

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14
Q

In which direction is the leading strand produced?

A

In the 5’ to 3’ direction

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15
Q

What are formed by the discontinuous productions of the lagging strand?

A

Okazaki fragments

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16
Q

What joins the Okazaki fragments together?

A

DNA Ligase

17
Q

What is epigenetics?

A

It is whether or not genes are expressed due to the structure of the chromatin

18
Q

Why is DNA replication semi-conservative?

A

Because the new DNA consists of 1 old and 1 new strand

19
Q

What is the role of topoisomerase in DNA replication?

A

Unfolds the helix and allows helicase to come in.

20
Q

What is the role of telomeres on chromosomes?

A

They prevent genes being lost during replication. They are repeated sequences so protect DNA from degregation

21
Q

Why do single stranded binding proteins bind during DNA replication?

A

To prevent the helix reforming

22
Q

What is the role of DNA primase?

A

Binds to DNA strand and synthesises an RNA primer at the replication fork

23
Q

What is the role of DNA Polymerase?

A

Synthesises a new DNA strand in a 5’ to 3’ direction by adding new nucleotides and then proof reads the nucleotides

24
Q

What is the function of chromatin?

A

To package DNA in order to fit it into a small volume and also protect DNA by preventing breakage. Also controls gene expression (epigenetics)

25
Q

What is a nucleosome?

A

A section of DNA that is looped around 8 histones twice each

26
Q

Why can a nucleoside enter a cell but a nucleotide can’t?

A

A nucleoside doesn’t contain the negative phosphate group that prevents the nucleotide from entering

27
Q

What is an exonuclease and an endonuclease?

A

EXONUCLEASE- cleave nucleotides from the end of a DNA stand

ENDONUCLEASE- cleaves nucleotides by breaking phosphodiester bonds in the middle of a chain

28
Q

Why does DNA polymerase contain an exonulcease domain?

A

To excise mismatched nucleotides that have been produced by the polymerase

29
Q

Why might there be a problem producing the final Okazaki fragment?

A

There is no room the bind the DNA primase to bind and so there’s no room to attach RNA primers meaning the final fragment can’t be produced

30
Q

What does the enzyme telomerase do?

A

Extends the chromosome