What is a linkage?

What is a linkage?

• A. Genes are on different chromosomes.
• B. Genes that undergo crossing over.
• C. A trait measurement method.
• D. Genes are linked if on the same chromosome; smaller distance = more closely linked.

Answer: (D)

Linkage means that genes are located on the same chromosome and tend to be inherited together because there isn't much chance for separation between them during meiosis. The key idea is that physical proximity on the chromosome makes it more likely that those gene variants stay together in the gametes. The closer two genes are, the smaller the chance that a crossing-over event will occur between them, so they are more tightly linked and co-segregate as a unit. If the genes are farther apart, crossing over is more likely between them, reducing the strength of the linkage and producing more recombinant types. In contrast, genes on different chromosomes assort independently, not as a linked unit. The other options don’t capture this idea: simply mentioning crossing over doesn’t define linkage, and a trait measurement method is unrelated to whether genes are linked.

Linkage means that genes are located on the same chromosome and tend to be inherited together because there isn't much chance for separation between them during meiosis. The key idea is that physical proximity on the chromosome makes it more likely that those gene variants stay together in the gametes. The closer two genes are, the smaller the chance that a crossing-over event will occur between them, so they are more tightly linked and co-segregate as a unit. If the genes are farther apart, crossing over is more likely between them, reducing the strength of the linkage and producing more recombinant types. In contrast, genes on different chromosomes assort independently, not as a linked unit. The other options don’t capture this idea: simply mentioning crossing over doesn’t define linkage, and a trait measurement method is unrelated to whether genes are linked.