2. Suppose you did a dihybrid cross of sweet peas using two F1 dihybrids each wi

Question

2. 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).

a. Red flowers with short pollen and Purple flowers with short pollen
b Red flowers with long pollen and Purple flowers with long pollen
c Purple flowers with short pollen and Red flowers with long pollen
d Purple flowers with long pollen and red flowers with short pollen


In the cross in number 2, which of the following observations suggests that the loci are linked.
a. A 9 : 3 : 3 : 1 phenotypic ratio was observed in the F2 offspring
b. A 9 : 3 : 3 : 1 phenotypic ratio was not observed in the F2 offpsring
c. An unusually high number of F2 offspring had parental phenotypes
d. Both b and c suggest linkage

Explanation / Answer

d. Purple flowers with long pollen (PPLL) and red flowers with short pollen (ppll) --------> parents as per your hint and option

a. A 9 : 3 : 3 : 1 phenotypic ratio was observed in the F2 offspring suggests that the loci are linked

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