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Here, B represents the allele for black hair and b represents the allele for white hair. If both the rabbits crossed had genotype Bb, what will be the phenotypic ratio for the observable monohybrid crosses (complete dominance)?



Responses
A 1:1:1:11:1:1:1
B 2:22:2
C 2:1:12:1:1
D 3:1

1 answer

In a monohybrid cross involving two rabbits with the genotype Bb (heterozygous for hair color), we can determine the expected phenotypic ratio for their offspring.

The possible gametes from each parent (Bb) will be:

  • B (black hair)
  • b (white hair)

When we set up a Punnett square for this cross:

       B       b
     ----------------
B |   BB      Bb
b |   Bb      bb

The genotypes of the offspring will be:

  • 1 BB (homozygous dominant, black hair)
  • 2 Bb (heterozygous, black hair)
  • 1 bb (homozygous recessive, white hair)

Now, let's derive the phenotypes from these genotypes:

  • BB and Bb both express the dominant phenotype (black hair).
  • bb expresses the recessive phenotype (white hair).

Counting the phenotypes:

  • Black hair (BB + Bb): 3 individuals
  • White hair (bb): 1 individual

Thus, the phenotypic ratio of black to white hair will be:

3:1

Therefore, the correct response is D 3:1.