Question

A gene (gene X) undergoes a mutation which converts if from wild-type to mutant. Then a second mutation in the gene Y occurs which causes the wild-type phenotype of the first gene (gene X) to be restored. Respectively, what are the appropriate designations for the two mutational events?
a. forward mutation, back mutation
b. forward mutation, suppressor mutation
c. reverse mutation, back mutation
d. reverse mutation, suppressor mutation
e. reverse mutation, forward mutation

Answer 1

Answer:

b. forward mutation, suppressor mutation

Explanation:

When the nucleotide sequence of an organism is altered, it is called as mutation. It can be caused by DNA damage or replication errors. In forward mutation, the wild type allele is converted to a mutant version such that the gene product is non functional or its not produced at all. Suppressor mutation is the second mutation which reverses the phenotypic effects of the previous mutation. This process is called as synthetic rescue.

Since here gene X was converted into a mutant form by the mutation, it had undergone forward mutation. When gene Y was mutated, the function of gene X was  restored which ultimately also restored the phenotype hence it is an example of suppressor mutation.