Question

If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the phenotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?

3 black : 1 orange
1 black : 0 orange
1 black : 1 orange
0 black : 1 orange
1 black : 3 orange

Answer 1

1 black : 1 orange

Step-by-step explanation:

This is a typical monohybrid cross involving a single gene coding for eye color in MendAlien. The allele for black eyes (B) is dominant over the allele for orange eyes (b). In an heterozygous state, Bb i.e. combination of both dominant (B) and recessive (b) alleles, the MendAlien will be phenotypically black.

In a cross between a heterozygous MendAlien (Bb) and an orange-eyed MendAlien (bb), two of the offsprings will have a Bb genotype and be phenotypically black-eyed which the other two will have a bb genotype and be phenotypically orange-eyed. Thus, a phenotypic ratio of 2 Bb : 2 bb will be obtained.

This is also equal to 1:1 i.e. 1 black-eyed : 1 orange-eyed.