$A$ guinea pig having black color,when crossed with a guinea pig having the same color,produced $80$ offspring,out of which $60$ were black and $20$ were white. Now,find out:
$(i)$ What is the possible genotype of the guinea pig?
$(ii)$ Which trait is dominant and which trait is recessive?
$(iii)$ What is this cross called,and what is its phenotypic ratio?

(A) $(i)$ Since the offspring show a $3:1$ ratio of black to white,both parents must be heterozygous. Thus,the genotype of both parents is $Bb \times Bb$.
$(ii)$ Black color is the dominant trait because it appears in the majority of the offspring,while white color is the recessive trait.
$(iii)$ This cross is called a monohybrid cross. The phenotypic ratio is $3:1$ (black:white).