Question

Using a punnett square workout the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and heterozygous male for a single locus.
   

Answer 1

Hint: First filial or progeny is the generation of hybrids comprising a cross among the genetically different individuals known as the parents. The filial generations are arranged in a sequence of mating such that the successive generations after a parental generation are represented by the symbol \[F1\] for the first filial generation, \[F2\] for the second filial generation, and so on. A cross among homozygous and heterozygous parents for a single locus will produce \[1:1\] ratio of phenotypic capabilities in the \[F1\] generation.

Complete answer:
Let us consider the example of Guinea pigs, a homozygous female with white colour (bb) is crossed with the heterozygous male having black colour (Bb). The male gamete will produce two kinds of gametes, i.e., B and b, at the same time as the female will produce only one kind of gamete, that’s b. The \[F1\] progeny will display each individual with black colour and white colour in a ratio of \[1:1\]. Here, the phenotypic, in addition to the genotypic ratio, can be \[1:1\].

Black colour: White colour
Genotypic ratio- \[Bb:bb{\text{ }}1:1\]
Phenotypic ratio- Black colour : white colour \[1:1\]

In the above figure, it’s clear that it is a cross between a heterozygous male with a homozygous female. In the \[F1\] generation the following phenotypic functions are observed:
\[\dfrac{1}{2}\] of the progeny are Heterozygous Tall (Tt).
Another \[\dfrac{1}{2}\] of the population is Homozygous short (tt).
Hence, the ratio for phenotypic ratio is equal to the genotype ratio, that is \[2:2\] or \[1:1\]

Note:
The filial generation is represented with the symbol F. Successive generations of progeny in a sequence of crosses, beginning with two specific individuals and selfing or intercrossing the progeny of every new \[\left( {F1;{\text{ }}F2;...} \right)\] generation. The offspring of distinctly different parents will produce a new and uniform phenotype with a combination of traits from the parents.