Question

22. Assume that the third codon within a particular ORF is AGA. Provide a singlebase substitution (point mutation) in this codon that causes a missense mutation AND ALSO is classified as a transition mutation?

23. How many possible singlebase substitutions (point mutations) in the codon above would cause a silent mutation?

24. Provide a singlebase substitution (point mutation) in the codon that would cause a nonsense mutation.

Answer 1

22.Missense mutations are point mutations that happenin a change in the codon resulting in the formation of a different protein.Transition mutation is that mutation where a purine is replaced by a purine or a pyrimidine is replaced by a pyrimidine.

AGA-codes for arginine, a point mutation in G to A gives AAA which codes for lysine.

23. Silent mutations that are possible in AGA without change in amino acid is 1(Arginine is coded by AGA or AGG).

24. Nonsense mutation results in a stop codon, UAG, UGA OR UAA.So a singlebase substitution would be A to U, AGA to UGA.