Question

In a certain species of animals, black fur (B) is dominant over brown fur (b). Show the possible ratio of genotypes and phenotypes of the offspring of the pure breeding different coloured parents?

Answer 1

In a heterozygous the trait which is expressed is known as the dominant trait. Black coloured animals will have phenotype BB. Recessive genotype is bb which will express brown colour. The pure breeding of different coloured animals will occur on breeding homozygous dominant with homozygous recessive.

Complete Answer:
The male animal is a homozygous male having black fur and having BB as its genotype. The female has brown fur and has bb genotype.
When these two are bred, the offspring of F1 generation:
The male gamete is B
The female gamete is b
When the two are crossed BXb, the offspring produced is Bb.

| B (male)
---|---
B(female)| Bb(black)

It is a heterozygous dominant Bb and has black fur. Their genotype will be Bb.

Additional information:
1. Phenotype: A physically observable character or property of an organism which is present in a species is called phenotype. Phenotype in an organism is determined by its genotype. Phenotype includes the appearance of the organism, development, and behaviour. For example, the characters used by Mendel to study the genetics of pea plants such as seed colour, seed coat colour, seed shape, pod shape, etc.
2. Genotype: A set of heritable genes in organisms which is passed down from parents to offspring is called genotype. The genes determine the characteristics that are visibly observable in organisms; these characters can be height, hair colour, etc.

Note: According to Mendel’s laws, when a homozygous dominant parent crosses over with a homozygous recessive parent, the offspring produced are heterozygous. The phenotype depends on the genotype of an organism. This proves the law of dominance.