Question

Which of the following can produce a frameshift in translation that changes the final genetic product?

a. deletion

b. a premature stop codon

c. a base por substitution

d. all of the above

Answer 1

Answer- a. Deletion

Explanation- Deletion is the type of point mutation in which single base is deleted from DNA and mRNA also lacks that base. During translation, codons are readed as nonoverlapping and of one base is deleted then open reading frame shifts back by one nucleotide. So that, from the site of Deletion, open reading frame of mRNA changes and amino acid sequence also changes. This is known as frameshift mutation. Frameshift mutation also occur when base is inserted into DNA. When insertion mutation occurs then open reading frame of mRNA shifts forward by one nucleotide and Amino acid sequence changes from the site of mutation.

So that deletion mutation can produce a frameshift in translation that changes the final genetic product.

Wrong options-

b. A premature stop codon- when point mutation results in change of codon into stop codon is known as nonsense mutation. In point mutation, due to base pair substitution amino acid codon is changed to one of the stop codon (UAA/UAG/UGA) and when this codon comes in ribosome during translation it is recognized by release factors and translation stops. Due to formation of premature stop codon short polypeptide is synthesized which is not functional. Premature stop codon does not causes frameshift mutation because open reading frame of mRNA is not changed.

c. A base pair substitution- base pair substitution can not result in frameshift mutation because in this type of mutation instead of correct nucleotide, wrong nucleotide is substituted during replication or by mutagens like physical or chemical. As base pair is substituted, open reading frame is not changed but only single amino acid change occurs at the site of mutation.