Question

Which of these mutations causes shortened protein with a long sequence of a substituted amino acid?

• A. Missense substitution of one nucleotide
• B. Insertion of two nucleotides
• C. Deletion of three nucleotides
• D. Silent substitution of four nucleotides
• E. Nonsense substitution of five nucleotides

Answer 1

The correct option is A Missense substitution of one nucleotide

Mutations affect large sections of DNA, others affect only certain points along the DNA strand. These small, specific mutations are called point mutations. Functionally point mutations are categorized as non-sense, missense, and silent mutations. Missense substitution of one nucleotide causes shortened protein with a long sequence of a substituted amino acid. For example, sickle-cell disease. The replacement of A by T at the 17th nucleotide of the gene for the beta chain of hemoglobin changes the codon GAG (for glutamic acid) to GTG (which encodes valine). Thus the 6th amino acid in the chain becomes valine instead of glutamic acid.