Question

On the planet Proboscide, there are elephants that are the size of flies. They genomic makeup is also very similar to the genomic make up of earth drosophila. There are two genes of interest for the elephants. They are PNT, and WGT.

The PNT gene produces two phenotypes, those elephants that like to eat peanuts and wild types that do not.

The WGT gene produces a wild-type phenotype of elephants near mean-weight, and a mutant phenotype where the weights are extreme (very heavy). Both genes have two alleles at their loci.

The mode of inheritance for the WGT gene is autosomal dominant, homozygous lethal. The mode of inheritance for the PNT gene is autosomal recessive. The two genes are unlinked.

In a cross between a male elephant with both extreme weight and that likes peanuts, and female elephant with wild-type phenotypes for both loci (true breeding at each locus)offspring are produced. Among these offspring, two elephants, both with extreme weight and wild-type PNT phenotypes (don't like peanuts) are crossed. In an F₂ offspring pool of approximately 1000 elephants, the most likely pairs of phenotype counts are:

A. (Phenotype 01, Phenotype 02) Count
(WGT, PNT) 500
(WGT, +) 500
(+, PNT) 0
(+, +) 0

Here, + is the wild-type phenotype at for the repsective gene.

B. (Phenotype 01, Phenotype 02) Count
(WGT, PNT) 570
(WGT, +) 180
(+, PNT) 187
(+, +) 62

Here, + is the wild-type phenotype at for the respective gene.

C. (Phenotype 01, Phenotype 02) Count
(WGT, PNT) 333
(WGT, +) 334
(+, PNT) 167
(+, +) 162

Here, + is the wild-type phenotype at for the repsective gene.

D. (Phenotype 01, Phenotype 02) Count
(WGT, PNT) 0
(WGT, +) 681
(+, PNT) 0
(+, +) 319

Here, + is the wild-type phenotype at for the repsective gene.

E. (Phenotype 01, Phenotype 02) Count
(WGT, PNT) 252
(WGT, +) 252
(+, PNT) 240
(+, +) 261

Here, + is the wild-type phenotype at for the repsective gene.

Answer 1

An autosomal dominant mode of inheritance suggests that one copy of the mutant allele is sufficient to express its corresponding phenotype in the individual. On the other hand, an autosomal recessive mode of inheritance is suggestive of the fact that it would require 2 copies of the mutant allele to express its corresponding phenotype in the individual.

Therefore the correct answer is C.