mutation - lecture 9

Question 1

What happens in somatic mutations?

Answer 1

Passed onto new somatic cells via mitosis

Question 2

What happens in germ - line mutations?

Answer 2

Mutations passed on to approx half members on the next generations

Question 3

what is a transition mutation?

Answer 3

Change from a purine to a purine or pyrimidine to pyrimidine

Question 4

what is a transversion mutation?

Answer 4

change from a purine to a pyrimidine or vica versa

Question 5

How do point mutations occur?

Answer 5

• DNA strands separate for replication
• T base pairs with G. Leading to wobble, an incorporated error
• At the next round G pairs with C , leading to mutation

Question 6

Depurination

Answer 6

Loss of a purine base, produces an apurinic site.

The apurinic site cannot provide a template for a complementary base. Incorrect nucleotide synthesized

Question 7

The side effects of depurination

Answer 7

Nucleotide with incorrect base incorporated

Question 8

Deamination

Answer 8

loss of an amino group

Question 9

The effects of deamination

Answer 9

can convert bases into one another

Question 10

What can UV radiation do?

Answer 10

Form a pyrimidine dimer: two thymine bases block replication

Question 11

strand slippage - what happens when the newly synthesised strand loops out?

Answer 11

Addition of one nucleotide on the new strand

Question 12

strand slippage - what happens when the template strand loops out?

Answer 12

omission of one nucleotide on the new strand

Question 13

What happens when homologous chromosomes cross over unequally?

Answer 13

One crossover has insert and other has deletion

Question 14

What is fragile X?

Answer 14

FMR1 gene - CGG repeat expansion

Question 15

What does Fragile X lead to?

Answer 15

• learning disabilities
• cognitive impairment
• males more affected

Question 16

What is the repeat expansion mechanism?

Answer 16

A hair pin forms on the newly synthesised strand . Causes part of the template to be replicated

Question 17

Why is male mutation rate higher?

Answer 17

male germ line replicates more constantly

Question 18

Mutation rates

Answer 18

higher for species with small genomes

Question 19

forward mutation definition

Answer 19

wild type to mutant

Question 20

reverse mutation definition

Answer 20

mutant type to wild type

Question 21

missense mutation

Answer 21

new wrong codon encodes incorrect amino acid

Question 22

nonsense mutation

Answer 22

new codon is a stop codon , premature termination of translation

Question 23

silent mutation

Answer 23

new codon encodes same amino acid

Question 24

Intragenic suppressor mutation

Answer 24

• missense muation alters a codon

- second mutation at different site in the same gene may restore the original amino acid

Question 25

Intergenic suppressor mutation

Answer 25

Base sub at site in another gene, which encodes tRNA, alters the anticodon or the RNA. Can pair with the mutation and incorporated into the sequence