What is depicted from the results of the test cross given here below? Round = 50%, Wrinkled = 50%.
Correct answer: A. The tested individual was heterozygous dominant
- A. The tested individual was heterozygous dominant
- B. The tested individual was heterozygous recessive
- C. The tested individual was homozygous dominant
- D. The tested individual was homozygous recessive
Explanation
The results of the test cross yield a 1:1 ratio of round to wrinkled seeds, indicating that the tested individual must be heterozygous dominant (Rr). This is because the offspring include both phenotypes, suggesting that the tested individual's genotype includes one dominant allele (R) and one recessive allele (r). If the individual were homozygous dominant (RR), all offspring would be round, and if it were homozygous recessive (rr), all offspring would be wrinkled. Therefore, the only explanation consistent with the observed results is that the tested individual was heterozygous dominant.
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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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