In Mendel's experiments with garden pea, round seed shape (RR) was dominant over wrinkled seeds (rr), yellow cotyledon (YY) was dominant over green cotyledon (yy). What are the expected phenotypes in the F2 generation of the cross RRYY × rryy?
Correct answer: B. Round seeds with yellow cotyledons, wrinkled seeds with yellow cotyledons, round seeds with green cotyledons, and wrinkled seeds with green cotyledons
- A. Round seeds with yellow cotyledons, and wrinkled seeds with green cotyledons
- B. Round seeds with yellow cotyledons, wrinkled seeds with yellow cotyledons, round seeds with green cotyledons, and wrinkled seeds with green cotyledons
- C. Only round seeds with green cotyledons
- D. Only wrinkled seeds with yellow cotyledons
Explanation
The correct answer is that the F2 generation will have four phenotypes: round seeds with yellow cotyledons, round seeds with green cotyledons, wrinkled seeds with yellow cotyledons, and wrinkled seeds with green cotyledons. This is due to the independent assortment of alleles during gamete formation, as explained by Mendel's laws. The F1 generation from the initial cross (RRYY × rryy) will all be heterozygous (RrYy), displaying the dominant traits (round and yellow). When these F1 individuals are crossed, the alleles segregate and recombine, resulting in the four phenotypic combinations in the F2 generation.
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About Inheritance
Mendel's laws explain segregation, independent assortment and the prediction of genetic ratios using alleles, genotypes and phenotypes. The chapter also covers linked genes, recombination and crossing over during meiosis, then applies pedigree reasoning to X-linked recessive traits, which show different inheritance patterns in males and females.
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