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Flashcards in DNA Deck (30)
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1

How is DMA packaged in chromosomes?

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

2

What is a gene?

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

3

What are the 3 stages in DNA replication?

Initiation, Elongation and termination

4

In what direction does DNA polymerase read?

From the 3' to 5' only

5

What is the human genome?

The entire DNA sequence for humans (24 chromosomes)

6

What is the difference between a nucleoside and a nucleotide?

A NUCLEOSIDE has no phosphate group attached.

7

What is the important of nucleosides?

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

8

What does DNA and RNA stand for?

DNA = deoxyribonucleic acid
RNA = Ribonucleic acid

9

What are the 2 purine bases?

Adenine and Guanine

10

What are the 3 pyrimidine bases?

Thymine and Cytosine and uracil

11

What is the difference between purines and pyrimidines?

Purines are bigger as they have 2 loops

12

What bonds join the sugar phosphate backbone?

Phosphodiester bonds

13

What enzyme unwinds the DNA strands during replication?

DNA Helicase

14

In which direction is the leading strand produced?

In the 5' to 3' direction

15

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

Okazaki fragments

16

What joins the Okazaki fragments together?

DNA Ligase

17

What is epigenetics?

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

18

Why is DNA replication semi-conservative?

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

19

What is the role of topoisomerase in DNA replication?

Unfolds the helix and allows helicase to come in.

20

What is the role of telomeres on chromosomes?

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

21

Why do single stranded binding proteins bind during DNA replication?

To prevent the helix reforming

22

What is the role of DNA primase?

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

23

What is the role of DNA Polymerase?

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

24

What is the function of chromatin?

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

What is a nucleosome?

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

26

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

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

27

What is an exonuclease and an endonuclease?

EXONUCLEASE- cleave nucleotides from the end of a DNA stand
ENDONUCLEASE- cleaves nucleotides by breaking phosphodiester bonds in the middle of a chain

28

Why does DNA polymerase contain an exonulcease domain?

To excise mismatched nucleotides that have been produced by the polymerase

29

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

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

What does the enzyme telomerase do?

Extends the chromosome