Under which circumstance does Mendel’s principle of independent assortment hold?

Question

BlackTom AI · Accepted Answer

The question asks about the circumstance under which Mendel’s principle of independent assortment holds. Here are the options analyzed one by one.
Option 1: 'only when traits are tightly linked (close together) on the same chromosome.' This is not consistent with independent assortment. When genes are tightly linked on the same chromosome, they tend to be inherited together and do not assort independently; instead, they show linkage unless recombination occurs. So this statement describes a situation contrary to independent assortment.
Option 2: 'only when there is crossing over.' Crossing over during meiosis can break linkage between genes on the same chromosome, contributing to recombination, but independent assortment itself is a principle about allele segregation into gametes and is most reliably observed when genes are on different chromosomes or are far apart on the same chromosome, allowing recombination to randomize combinations. This option misstates the core requirement by tying independence exclusively to crossing over, which is not the defining condition for the principle.
Option 3: 'only for simple traits.' The term 'simple traits' is vague and does not define the genetic mechanism behind independent assortment. The principle relates to how alleles at different loci assort during gamete formation, regardless of whether the traits are categorized as simple or complex, so this option is not correct.
Option 4: 'only when traits are on different chromosomes.' This aligns with the classic statement of Mendel's principle of independent assortment: genes located on different chromosomes assort independently because their sorting into gametes is unlinked to one another during meiosis. When loci are on separate chromosomes, their inheritance is effectively independent, barring other complicating factors.
In summary, the questions’ options contrast different genetic scenarios—linkage, recombination, trait simplicity, and chromosomal location—with independent assortment being most accurately described as occurring when loci reside on different chromosomes. The option that matches this scenario is the final one.

Under which circumstance does Mendel’s principle of independent assortment hold?单项选择题

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