Suppose you did a dihybrid cross of sweet peas using two F1 dihybrids each with

Question

Suppose you did a dihybrid cross of sweet peas using two F1 dihybrids each with a genotype of PpLl. The P gene confers purple flowers and it is dominant over the p gene which confers red flowers in the homozygous condition. The L gene confers long pollen grains while the recessive ll genotype confers short pollen grains. As a result of the cross you did, you got the following numbers of different phenotypes of offspring: 148 Purple flowers with long pollen 10 Purple flowers with short pollen 14 Red flowers with long pollen 143 Red flowers with short pollen Which of the above are parental (non-recombinant) offspring? This would also apply to the parents, the original true-breeding P generation from which the dihybrids were bred. (Hint, one parent strain was homozygous dominant at both loci and the other was homozygous recessive at both loci).

Explanation / Answer

The original parents, one was homozygous dominant at both loci (PPLL) and the other was homozygous recessive at both loci (ppll). So, one of the parents' phenotype is Purple flower and long pollen (PPLL) and the other is parent red flower short pollen grain(ppll). From the F1 generation, PpLl was chosen. In the F2 generation, according to Mendel, the self-crossing of two dihybrid heterozygous individuals result in the offsprings with genotypic ratio 9:3:3:1. Since we can observe clearly that Mendelian ratio is not maintained here, it can be concluded that there is some level of linkage in the inheritance of these two genes.

The offsprings that have parental genotype in F2 generation(parents from F1 generation) are the ones with Purple flowers long pollen.

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