Mendel studied seven genes; six were on different chromosomes. What does this imply about their inheritance?

• A. Alleles assort independently
• B. They are completely linked
• C. They show incomplete dominance
• D. They cannot recombine

Answer: (A)

Independent assortment is being tested here. When genes reside on different chromosomes, the two alleles for each gene segregate into gametes independently of the alleles for other genes. During meiosis, the orientation of each chromosome pair is random, so the allele an organism passes for one gene is not tied to which allele it passes for another gene on a different chromosome. With six genes on separate chromosomes, this creates many possible allele combinations in gametes—2 choices for each gene, resulting in 2^6 different combinations. That’s why their inheritance happens independently rather than predictably linking with one another. The idea that they’re completely linked would imply they tend to be inherited together, which isn’t the case here. Incomplete dominance describes how a heterozygote’s phenotype appears, not how alleles segregate. And while recombination can occur within a chromosome, genes on different chromosomes sort into gametes independently regardless of recombination.