I have an urgent question as I have an exam tomorrow. I was skimming some past exam papers and one question came up which has me completely confused.

A cross was made between a pure breeding diploid pea plant with round, yellow seeds and a pure breeding diploid plant with wrinkled, green seeds. R and r for round and wrinkled respectively, and Y and y for yellow and green respectively. Assume dominant allele of each gene is upper case, and that the two genes are on different chromosomes and so are independently assorting.

a) Give genotypes of two pure breeding parents

RRYY, rryy

b) Give the genotype of resultant F1 progeny


c) Give the genotype and respective frequency of the gametes produced by the F1 individual and indicate whether the gametes are parental or recombinant.

This is the question I am having trouble with and confused about

The reason I am confused is primarily I do not understand what is being asked when referring to the "gametes produced". Is this an F1xF1 cross and the question is asking about the F2 generation? I assumed not as the next question is:

Two of the F1 individuals obtained from the above parental cross were crossed to obtain the F2 generation

d) Give the phenotypes of the F2 progeny and their ratios

If someone could please shed some light on this it would be much appreciated


1 Answer 1


Gamate is a haploid germ cell produced by either male or female parent. In your question,two homozygous dominant and recessive parants produce RY and ry gamates respectively. F1 would have four types of gamates if we think about their genotype.They should have any one of RY, Ry, rY, ry as their genotype. RY and ry are parental gamates. They have the genotype of the gamates that F1's homozygous parents produced. Other two are recombinant genotype. Since they behave independently, you can go with mendelian genetics and draw a punnett squre.write RY Ry rY ry horizontally and vertically then get the F2 cross genotypes. Dominant genotypes will determine the phenotype.


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