Mutation: complementation, gene structure and gene function

Question 1

What are the two different types of recessive loss of function gene mutations as defined by Muller.

Answer 1

Null mutations and hypomorphic mutations.

Question 2

What is a null mutation?

Answer 2

When a homozygous mutant/mutant has the same phenotype as a mutant/deletion. Thus, the mutant allele has no gene function.

Question 3

What defines a hypomorph?

Answer 3

When a homozygous mutant/mutant has a phenotype more similar to the wildtype than a mutant/deletion. Thus, the mutant allele has reduced gene function.

Question 4

What is the name for a dominant loss of function mutation as defined by Muller?

Answer 4

A haploinsufficient mutant.

Question 5

What defines a haploinsufficient mutant?

Answer 5

Mutant/wildtype has a dominant phenotype and this phenotype is the same as deletion/wildtype. (one wildtype copy is not enough for a normal phenotype)

Question 6

What are the three types of dominant mutations that alter gene function?

Answer 6

Antimorphic mutations, hypermorphic mutations, and neomorphic mutations.

Question 7

What defines an antimorphic mutant?

Answer 7

The mutant/wildtype has a more severe mutant phenotype than mutant/wildtype with an additional wildtype allele. Thus, the mutant allle antagonizes the wildtype allele.

Question 8

What defines a hypermorphic mutation?

Answer 8

Mutant/wildtype has a weaker phenotype than Mutant/ 2 copies of the wildtype. Thus, the mutant allele has increased wildtype activity.

Question 9

What defines a neomorphic mutation?

Answer 9

Mutant/wildtype is the same as mutant/2 copies of the wildtype. Thus, the mutant allele has a novel function that differs from the wildtype and adding a duplication of the wildtype allele has no effect on phenotype.