What observation would support the existence of linked genes?

What observation would support the existence of linked genes?

• A. They are always inherited together
• B. They show less recombination than unlinked genes
• C. They never recombine
• D. They are on different chromosomes

Answer: (B)

Linked genes are on the same chromosome, so they’re usually inherited together because crossing-over between them is less likely. The best observation for linkage is that they show a lower rate of recombination between them than genes that assort independently. In other words, their recombination frequency is less than that seen with unlinked genes, so parental allele combinations appear more often than recombinant ones. Crossing-over can still occur, so they aren’t always inherited together and aren’t forever stuck as a unit. If the genes were on different chromosomes, you’d expect about 50% recombination, which would not indicate linkage.

Linked genes are on the same chromosome, so they’re usually inherited together because crossing-over between them is less likely. The best observation for linkage is that they show a lower rate of recombination between them than genes that assort independently. In other words, their recombination frequency is less than that seen with unlinked genes, so parental allele combinations appear more often than recombinant ones. Crossing-over can still occur, so they aren’t always inherited together and aren’t forever stuck as a unit. If the genes were on different chromosomes, you’d expect about 50% recombination, which would not indicate linkage.