Question

An animal (guinea pig) having black colour is crossed with guinea pig having the same colour. They produced 100 offsprings, of which 75 were black and 25 were white. 

Find out 

(i) What is the possible genotype? 

(ii) Which trait is dominant and which is recessive?

Answer 1

Let BB/ Bb be the dominant color (black) of guinea pig and bb be the recessive trait which codes for white color of guinea pig. 

i) The possible genotype of the parent pigs is Bb i.e. the animals are heterozygously dominant as they produced offspring in the ratio of 3: 1. The 25 of the black pigs have the gene BB whereas the rest 50 of the black pigs have genes Bb and the white pigs have bb. 

ii) The trait coding for black color is dominant while the one coding for white is recessive.