Dihybrid Cross
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Problem: Predicting combinations of alleles in gametes of plants heterozygous for two traits.
| A pea plant is heterozygous for both seed shape and seed color. S is the allele for the dominant, spherical shape characteristic; s is the allele for the recessive, dented shape characteristic. Y is the allele for the dominant, yellow color characteristic; y is the allele for the recessive, green color characteristic. What will be the distribution of these two alleles in this plant's gametes? |
Assortment of Ss alleles
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The gametes from the SsYy parent will receive one of the two alleles Ss. Half will receive the dominant S allele, and half the recessive s allele. |
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Assortment of Yy alleles
| The gametes from the SsYy parent will also receive
one of the two alleles Yy.
Half will receive the dominant Y allele, and half the recessive y allele. |
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Possible combinations of alleles in gametes of plants heterozygous for two traits.
| Since alleles of different traits segregate independently during
gamete formation, there is the same probability that the Y (or y)
allele will segregate with the S allele as with the s allele.
Thus all four combinations of gametes (SY, Sy, sY, sy) are equally probable. |