DNA replication (Genetics 4)

Question 1

What must a cell do to divide?

Answer 1

Grow, copy its genetic material and split into two daughter cells

Question 2

What two major phases is the cell cycle divided into?

Answer 2

Interphase and mitotic phase

Question 3

What occurs during interphase

Answer 3

the cell grows and makes a copy of its DNA

Question 4

What occurs during the mitotic phase

Answer 4

the cell separates its DNA into two sets and divides its cytoplasm, forming two new cells

Question 5

Semi-conservative replication

Answer 5

DNA acts as a template for its own replication

Question 6

DNA Helicase

Answer 6

breaks the hydrogen bonds between nucleotides

Question 7

DNA Polymerase

Answer 7

synthesises DNA in the 5 to 3 direction

Question 8

DNA Topoisomerase

Answer 8

relieves tension in the DNA

Question 9

DNA Primase

Answer 9

syntheises RNA primers

Question 10

Ribonucleases

Answer 10

degrades RNA Primers

Question 11

DNA Ligase

Answer 11

joins DNA fragments

Question 12

Telomerase

Answer 12

replicates the ends of the chromosome

Question 13

Single-Strand Binding Protein

Answer 13

Binds and keeps both strands apart from each other

Question 14

Leading Strand

Answer 14

Continuous DNA production

Question 15

Lagging Strand

Answer 15

Discontinuous DNA production

Question 16

Okazaki fragments

Answer 16

short DNA sequences produced on the lagging strand

Question 17

Sliding clamp

Answer 17

Ring shaped protein, binds DNA polymerase to the DNA template

Question 18

DNA primase

Answer 18

Found on the lagging strand, attaches RNA to the template

Question 19

DNA polymerase III

Answer 19

adds nucleotides until it reaches the previous primer

Question 20

RNase H

Answer 20

digests the RNA primer, leaving a gap

Question 21

DNA polymerase

Answer 21

fills in the gaps between two okazaki fragments

Question 22

DNA ligase

Answer 22

Joins two fragments together on the lagging strand

Question 23

Telomeres

Answer 23

Repetitive units at the end of chromosomes

Question 24

Function of Telomeres

Answer 24

Protect the internal regions of the chromosomes/ worn down during DNA replication

Question 25

DNA polymerase A

Answer 25

doesn’t require a primer, has its own primase enzyme- therefore preventing the shortening of the DNA strand

Question 26

How can DNA become damaged?

Answer 26

UV light, ionising radiation, toxic chemical agents, reactive oxygen

Question 27

Double stranded breaks

Answer 27

Chromosomes split into two caused by environmental factors such as high energy radiation

Question 28

Gain of function

Answer 28

Change in DNA that leads to increased/ alternative activity

Question 29

Loss of Function

Answer 29

Change in DNA that leads to decreased activity

Question 30

Splice-site mutation

Answer 30

A splice site mutation is a genetic mutation that inserts, deletes or changes a number of nucleotides in the specific site at which splicing takes place

Question 31

Excision

Answer 31

the first stage of mechanism of DNA repair; recognition and removal of damage (exonuclease)

Question 32

Repair

Answer 32

The second stage of DNA repair-synthesis of missing DNA (DNA polymerase)

Question 33

Joining

Answer 33

The final stage of DNA repair, sealing the fragments (DNA Ligase)

Question 34

Thymine Dimers

Answer 34

Two Thymine Bases become covalently bonded to each other

Question 35

What is the difference between DNA polymerase III and DNA polymerase I

Answer 35

DNA polymerase III: Synthesises the nucleotides on the lagging strand
DNA polymerase I: fills in the gaps

Question 36

What is Depurination?

Answer 36

DNA mutation, removal of an Adenine or Guanine base

Question 37

What is Deamination?

Answer 37

DNA mutation, removal of ammonia changing cytosine to Uracil

Question 38

What do Thymine Dimers arise from?

Answer 38

UV radiation

Question 39

What is nonsense mediated decay?

Answer 39

a process during translation that detects transcripts with
premature stop codons and degrades them.

Question 40

What direction is DNA usually synthesised in?

Answer 40

5’ to 3’ direction

Question 41

What is a primer?

Answer 41

A short section of RNA

Question 42

How often does DNA polymerase make a mistake?

Answer 42

once every 10 to the 7 nucleotide pairs

Question 43

What are the 3 different point mutations?

Answer 43

Silent, Missense and Nonsense

Question 44

What is Nonsense Mediated Decay?

Answer 44

a process during translation that detects transcripts with
premature stop codons and degrades them.

Question 45

What factors effect whether an indel mutation will be tolerated?

Answer 45

Whether it’s a frameshift, its size and its location

Question 46

What is a splice site mutation?

Answer 46

A genetic mutation that changes the number of nucleotides at the area where splicing occurs

Question 47

What is non-homologous end joining?

Answer 47

The ends are ‘polished’ to produce ‘blunt ends’
» The ends are then joined (DNA ligase)

Question 48

What is the problem with non-homologous end joining?

Answer 48

there will be a resultant loss in nucleotides, the consequence depends on its position within the genome

Question 49

When is non-homologous end joining usually used?

Answer 49

for rapidly dividing cells

Question 50

Homologous end joining

Answer 50

recombination between two corresponding regions of the two alleles, it is a complete repair which means that no sequences are lost

Question 51

What is the problem with homologous end joining?

Answer 51

It is much more slower and therefore less useful for rapidly dividing cells but it is much more accurate

Question 52

What is a conservative substitution?

Answer 52

similar amino acid R group and size

Question 53

What is a radical substitution?

Answer 53

New amino acid R group that is different in charge and size