Question

3.Original DNA sequence: 3' TACCGCTTACGTCTGATCGCT 5'

Answer 1

3. The original sequence

TAC - CGC - TTA - CGT - CTG - ATC - GCT

codes for

tyr - arg - leu - arg - leu - ile - ala

while the mutated sequence codes for

TAC - CGC - TTA - TTA - TTA - CGT - GCT - GCT - ATC - GCT

tyr - arg - leu - leu - leu - arg - ala - ala - ile - ala

There are several frameshift mutations involved here:

• the first inserts 6 bases (TTA - TTA)

• the second inserts 1 base (G) before the CTG triplet (underlined)

• the third inserts 2 bases (CT) after the CTG triplet

4. The original sequence is the same as before. The mutated sequence

TAC - CGC - TAA - TTA - TTA - CGT - GCT - GCT - ATC - GCT

codes for

tyr - arg - STOP - leu - leu - arg - ala - ala - ile - ala

Then

• there is a (nonsense) point mutation that swaps T for A in the original TTA triplet (nonsense since it produces a stop codon that would halt replication/expression)

• there is a frameshift mutation that inserts 3 bases (TTA)

as well as two other frameshift mutations that also occurred in the previous part.