Let 'B' represent the dominant allele for black face colour.
This biology question covers important biological concepts and processes. The step-by-step explanation below helps you understand the underlying mechanisms and reasoning.
ScanSolve AI Answer
Here is the solution to the monohybrid crossing problem:
Let 'B' represent the dominant allele for black face colour.
Let 'b' represent the recessive allele for white face colour.
Parent A (purebred black-faced ram) has genotype BB.
Parent B (purebred white-faced ewe) has genotype bb.
1.3.1. Write down the genotype of parent B.
The genotype of parent B is bb.
1.3.2. Indicate whether parents A and B are homozygous or heterozygous.
Parents A and B are both homozygous.
1.3.3. Give a reason for the answer to QUESTION 1.3.2.
They are described as purebred, which means they have two identical alleles for the trait (homozygous). Parent A is homozygous dominant (BB) and Parent B is homozygous recessive (bb).
1.3.4. Identify the phenotype in the F2 generation, as represented by F, G and H.
F1 generation (C): When BB is crossed with bb, all F1 offspring (C) will have the genotype Bb. Their phenotype will be black-faced.
F2 generation: The F2 generation results from crossing F1 x F1 (Bb x Bb).
Punnett Square for F2:
| | B | b |
|---|-----|-----|
| B | BB | Bb |
| b | Bb | bb |
The genotypes in F2 are BB, Bb, Bb, bb.
The diagram shows BB, F, G, H.
Therefore, F and G represent Bb genotypes, and H represents the bb genotype.
Phenotype of F (Bb): Black-faced*
Phenotype of G (Bb): Black-faced*
Phenotype of H (bb): White-faced*
1.3.5. Indicate the genotypic and phenotypic ratio in the F2 generation.
Genotypic ratio: $1 \text{ BB} : 2 \text{ Bb} : 1 \text{ bb}$
Phenotypic ratio: $3 \text{ Black-faced} : 1 \text{ White-faced}$
