Question

heterozygous for red antennas, what are the predicted Phenotypic outcomes of their offspring? (hint: a punnett square will help you determine this).
In butterflies, having red antennas (denoted by “R”) is dominant to having white antennas (denoted by “r”). If both parents are heterozygous for red antennas, what are the predicted Genotypic outcomes of their offspring? (hint: a punnett square will help you determine this).

All the offspring of a cross between a black-eyed mendelien and an orange-eyed mendelien have black eyes. What is the expected F2 phenotypic ratio of a cross between two F1 black-eyed mendeliens?
A) 1 black-eyed:1 orange-eyed
B) 3 black-eyed:1 orange-eyed
C) 1 black-eyed:3 orange-eyed
D) 1 black-eyed:0 orange-eyed

Answer 1

Answer:

1. 3 red antennas: 1 white antenna

2. B) 3 black-eyed:1 orange-eyed

Explanation:

1). According to the first question, a gene coding for antenna color in butterflies is involved. Red antennas (“R”) is dominant to white antennas (“r”). Hence, a butterfly with Rr will be phenotypically red.

According to this question, If both parents are heterozygous for red antennas i.e. Rr (red antenna) × Rr (red antenna), the following gametes will be produced: R and r. Using these gametes in a punnet square (see attached image), the following phenotypic ratio of offspring is produced:

3 red antennas (RR, Rr, Rr) : 1 white antenna (rr)

2. In the second question, all the offspring of a cross between a black-eyed mendelien (BB) and an orange-eyed mendelien (bb) have black eyes (Bb). In a cross between two F1 black-eyed mendeliens i.e. Bb × Bb, the following proportion of offspring is produced:

BB, Bb, Bb, bb

Hence, a phenotypic ratio of 3 black-eyed: 1 orange-eyed