Question

The sequence of nucleotides in an mRNA is 5’AUGACCCAUUGGUCUCGUUGGCUGAAGUCA 3’.

Answer 1

Answer:

The polypeptide chain will be six amino acids long after mutation has occurred on the mRNA strand.

Explanation:

The mRNA sequence to be transcribed into the polypeptide chain

5’AUGACCCAUUGGUCUCGUUGGCUGAAGUCA 3’

If hydroxylamine were applied to cells and caused mutation changing G to A at position 20. It will lead to a change in the amino acid to be produced and also a change in the expected number of amino acids.

Thus, if we have: 5’AUGACCCAUUGGUCUCGUUGGCUGAAGUCA 3’

A change from G to A will change the triplet codon to UAG which is one of the three stop codons signifying the end of translation, thus there will be six amino acids formed.

Answer 2

Answer:

Ths change represents a mutation of tryptophan (W) to a stop codon: W  to a stop codon  

Explanation:

Messenger RNAand protein sequence (below):

AUG ACC CAU UGG UCU CGU UGA CUG AAG UCA

  M     T      H      W       S      R     " W  "   L        K      S

Since the mutagen changes the sequence to produce a stop codon at position 20 of the DNA, it is expected the following polypeptide sequence:

AUG ACC CAU UGG UCU CGU UGA CUG AAG UCA

  M      T      H      W       S      R       -  

Stop codons such as UAG, UAA and UGA mark the end of the protein coding sequence