Biology

Stella Orr

24 February, 18:01

Trekian Fur is a dominant trait. Trekkies (on the planet Gomaz) from a pure-breeding population with the Trekian Fur gene are scored for their phenotypes. The two alleles at the Trekian Fur gene are T (dominant) and t (recessive).

80% of the Trekkies from this colony (genotype TT) have Trekian Fur; 20% of the Trekkies look wild-type.

Also, the penetrance of the Trekian Fur phenotype is 65% in the heterozygous Trekkies.

Pure breeding wild-type Trekkies (tt) show the Trekian Fur phenotype 10% of the time. Thus, the penetrance of Trekian Fur is 10% in homozygous wild-type Trekkies.

Problem: If two heterozygotes for the Trekian Fur gene (Tt x Tt) are crossed, what proportion of the offspring are expected to show the Trekian Fur phenotype?

A. 80%.

B. 55%.

C. 45%.

D. 50%.

E. 20%.