Guinea pig having black colour when crossed with guinea pig having same colour produceds 80offspring , out of which 60 wear black and 20 wear white now find out (a) what is the possible genotype of the guinea pigs? (b) which state is dominant and which state is recessive (c ) what is the cross called as and what is the phenotypic ratio ?
Answers
Answer:
(a) The possible genotype of the guinea pigs : BB, Bb & bb
(b) Black is dominant over white.
(c) Monohybrid cross ; 3:1
Explanation:
(a) Since the phenotypic ratio is 60:20 which means 3:1 , the parents have to be heterozygous. ,that is, Bb.
B is the dominant allele which is responsible for black color whether it is present in homozygous (BB) or heterozygous (Bb) condition and b is the recessive allele which express white color when present in homozygous (bb) condition.
So, Bb X Bb gives genotypes BB,Bb and bb which are the possible genotypes for guinea pig.
(b) The frequency of occurrence of dominant trait is higher then the recessive trait in a population.The phenotypic ratio is 3:1 where 3 indicates Black color and 1 indicates white color.Since black is present in more number of offspings as compared to white ones, the dominant one is black color and recessive one is white color.
(c) It is involving cross between a single trait or character which is the color of guinea pig , therefore, it is a monohybrid cross.
Ratio of 60:20 gives the phenotypic ratio which is 3:1.
Answer:
a) The possible genotype of the guinea pigs : BB, Bb & bb
(b) Black is dominant over white.
(c) Monohybrid cross ; 3:1