17. Relationships between genes and genotype

Question 1

How are errors repaired on the spot?

Answer 1

• proofreading

* the DNA polymerase can go backwards 3’ to 5’ and cut out an error and replace the base

Question 2

What is the function of enzyme telomerase?

Answer 2

• extends the lagging strand (overhang)

* primer then attaches and DNA polymerase completes the replication

Question 3

What is the template for extension of lagging strand (overhang)?

Answer 3

Template used if RNA of telomerase

Question 4

What is the effect of having shorter telomeres?

Answer 4

• Werner Syndrome

- premature ageing

Question 5

Describe a mismatch repair

Answer 5

• during DNA replication, a nucleotide was mispaired and missed in proofreading
• Mismatch repair protein excise the mismatched nucleotide and some adjacent nucleotides
• DNA polymerase I adds the correct nucleotides
• DNA ligase then repairs the remaining nick

Question 6

Describe an excision repair

Answer 6

• A nucleotide is damaged
• the excision repair proteins excise the damaged nucleotides
and some adjacent nucleotides
• DNA polymerase 1 adds the correct nucleotides by 5’ to 3’ replication of the short strand

Question 7

What is PCR?

Answer 7

A technique which mimics DNA replication - Polymerase Chain Reaction

Question 8

What are the steps involved in PCR?

Answer 8

1. DNA is made single-stranded by heating to 95º

2. primers complementary to the ends of the region of interest are annealed (at 60-65º)

Question 9

Approximately how many bases do primers in PCR contain?

Answer 9

15~30 bases

Question 10

What is the function of taq polymerase?

Answer 10

A DNA polymerase that adds new bases complementary to the template DNA

Question 11

What is the difference between a prototroph and auxotroph?

Answer 11

• prototroph - grows on minimal media

* auxotroph - requires a supplement in the medium