Question

The schematic representation given below shows a DNA strand and two types of mutations in the DNA strand.

Original template

A

U

G

C

A

G

A

C

A

U

C

U

U

A

G

Met

Gln

Thr

Ser

Stop

 

Mutation I

A

U

G

A

A

G

A

C

A

U

C

U

U

A

G

Met

Lys

Thr

Ser

Stop

 

Mutation II

A

U

G

A

G

A

C

A

U

C

U

U

A

G

Met

Arg

His

Leu

1. Identify the type of mutation exhibited in I and II.
2. Which of the above mutation is more harmful? Give reason.

Answer 1

1. I is point mutation; II is Frame shift
2. II, as more codons are affected;
   It is extremely likely to lead to large-scale changes to polypeptide length and chemical composition/resulting in a non-functional protein that often disrupts the biochemical processes of a cell/incorrect amino acids are inserted/often premature termination occurs when a nonsense codon is read/frameshifts have very severe phenotypic effects.