Question

Part A: The following sequence encodes a protein in the virus genome: 5’ tctaaaatgtcagatgtaaagtgcacatcagtagtcttactctcagttttgtaacaactc 3’ 3’ agattttacagtctacatttcacgtgtagtcatcagaatgagagtcaaaacattgttgag 5’ How many amino acids long is the protein?

Part B: A base pair substitution (ie. a point mutation) that introduces a nonsense mutation could be introduced to the sequence encoding the protein in Part A. True/False

Answer 1

Part A

In the given DNA, the lower strand acting as the template strand for transcription. Hence the sequence of the mRNA produced by transcription is

5'- UCU AAA AUG UCA GAU GUA UUG UGC ACA UCA GUA GUC UUA CUC UCA GUU UUG UAA CAA CUC- 3'

In the given sequence, the third codon AUG is the start codon and 18th is the stop codon. Hence the protein has 15 amino acids. The amino acid sequence of the protein is

Met - Ser- Asp- Val- Leu- Cys- Thr- Ser- Val- Asp- Leu- Leu- Ser- Val- Leu- Stop.

Part B

Point mutation is the mutation happening in a single base and the base substitution, the replacement of an existing base with another base during DNA replication can lead to this. In nonsense mutation, the stop codon will insert into the coding region of a gene due to base substitution. there are three stop codons which are UAA, UAG, and UGA. In the given sequence, a base substitution in the twentieth base, substitution from A to T can cause nonsense mutation

Then the answer is TRUE