Mutation & Mutagenesis

Question 1

Define mutation

Answer 1

Change in nucleotide sequence of gene

Question 2

True or false: mutation is inheritable if reproductive cells DNA is affected

Answer 2

True —> natural selection

Question 3

Define polymorphism

Answer 3

A number of non-disadvantageous mutations in the population e.g. eye colour

Question 4

Define mutation rate

Answer 4

Rate at which DNA sequence changes

Question 5

How is a mutation rate calculated

Answer 5

Estimates indirectly: comparing AA sequences in proteins of different organisms and time divergence with common ancestor

Question 6

What is a pyrimidine

Answer 6

C & G bases

Question 7

What is a Purine

Answer 7

A & T bases

Question 8

What is a point mutation

Answer 8

A single base change in a sequence, has a tendency to back mutate

Question 9

What are the 4 types of point mutation

Answer 9

Transitions
Transversions
Insertion
Deletion

Question 10

Describe a transition mutation

Answer 10

A point mutation where a pyrimidine mutates to a pyrimidine or purine to purine

Question 11

Describe a transversion mutation

Answer 11

Py to Pu / Pu to Py

Question 12

Describe a deletion mutation

Answer 12

Deletion of a single base —> frame shift
Can also be a multi site mutation
No back mutation

Question 13

Describe an insertion mutation

Answer 13

Insertion of a single base —> frame shift
Can also be a multi site mutation
Tends to back mutate

Question 14

Many wild type microbes are prototrophic, define prototrophic

Answer 14

Can grow on minimal medium - more or less synthesises all of its requirements like proteins, nourishment etc.
Don’t need addition of specific compounds

Question 15

Humans are auxitriohic, define autotrophic

Answer 15

Require addition of specific compounds

Question 16

Give some examples of mutations in human disease

Answer 16

Sickle cell
Thalassaemia
PKU

Question 17

How is mutation linked to cancer

Answer 17

Occurs when mechanisms maintaining normal growth rates malfunction. Due to malfunctions in tumour-suppressor genes or caretaker genes. Mutations arise after life time exposure to carcinogens
Somatic mutations can act in combination with inherited mutations to cause cancer

Question 18

How are the BRCA-1/2 genes connected to hereditary breast cancer

Answer 18

Mutations in tumour suppressor genes, involved in repair of ds breakers in DNA, leads to them losing function thus increasing cells’ susceptibility to radiation damage.

Question 19

Define recessive (trait)

Answer 19

Both alleles must be mutant for mutant phenotype

Usually result from mutation that Inactivated the affected gene leading to partial/carrier or complete loss of function

Question 20

Define Dominant (trait)

Answer 20

Only one allele must be mutant. Heterozygous individuals exhibit mutant phenotype
Usually cause Gain of function (increases activity or new/inappropriate expression)

Question 21

What are leaky mutations

Answer 21

Mutations that are never lethal because mutant protein retains some functional activity

Question 22

Why does tautomerisation cause mutation

Answer 22

Molecule interact differently in their keto and enol forms and will bind with different bases