DNA

Question 1

How is DMA packaged in chromosomes?

Answer 1

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

Question 2

What is a gene?

Answer 2

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

Question 3

What are the 3 stages in DNA replication?

Answer 3

Initiation, Elongation and termination

Question 4

In what direction does DNA polymerase read?

Answer 4

From the 3’ to 5’ only

Question 5

What is the human genome?

Answer 5

The entire DNA sequence for humans (24 chromosomes)

Question 6

What is the difference between a nucleoside and a nucleotide?

Answer 6

A NUCLEOSIDE has no phosphate group attached.

Question 7

What is the important of nucleosides?

Answer 7

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

Question 8

What does DNA and RNA stand for?

Answer 8

DNA = deoxyribonucleic acid 
RNA = Ribonucleic acid

Question 9

What are the 2 purine bases?

Answer 9

Adenine and Guanine

Question 10

What are the 3 pyrimidine bases?

Answer 10

Thymine and Cytosine and uracil

Question 11

What is the difference between purines and pyrimidines?

Answer 11

Purines are bigger as they have 2 loops

Question 12

What bonds join the sugar phosphate backbone?

Answer 12

Phosphodiester bonds

Question 13

What enzyme unwinds the DNA strands during replication?

Answer 13

DNA Helicase

Question 14

In which direction is the leading strand produced?

Answer 14

In the 5’ to 3’ direction

Question 15

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

Answer 15

Okazaki fragments

Question 16

What joins the Okazaki fragments together?

Answer 16

DNA Ligase

Question 17

What is epigenetics?

Answer 17

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

Question 18

Why is DNA replication semi-conservative?

Answer 18

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

Question 19

What is the role of topoisomerase in DNA replication?

Answer 19

Unfolds the helix and allows helicase to come in.

Question 20

What is the role of telomeres on chromosomes?

Answer 20

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

Question 21

Why do single stranded binding proteins bind during DNA replication?

Answer 21

To prevent the helix reforming

Question 22

What is the role of DNA primase?

Answer 22

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

Question 23

What is the role of DNA Polymerase?

Answer 23

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

Question 24

What is the function of chromatin?

Answer 24

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

Question 25

What is a nucleosome?

Answer 25

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

Question 26

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

Answer 26

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

Question 27

What is an exonuclease and an endonuclease?

Answer 27

EXONUCLEASE- cleave nucleotides from the end of a DNA stand

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

Question 28

Why does DNA polymerase contain an exonulcease domain?

Answer 28

To excise mismatched nucleotides that have been produced by the polymerase

Question 29

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

Answer 29

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

Question 30

What does the enzyme telomerase do?

Answer 30

Extends the chromosome