If two loci are far apart on the same chromosome, what is expected during meiosis?

If two loci are far apart on the same chromosome, what is expected during meiosis?

• A. They will show recombination at a measurable rate and may assort independently.
• B. They will always stay together.
• C. They never recombine.
• D. They are unaltered by recombination.

Answer: (C)

Distance between two loci on the same chromosome matters for recombination. When they are far apart, crossing over during meiosis occurs frequently between them, so recombinant chromatids are produced in a substantial fraction of gametes. As this distance increases, the recombination frequency approaches 50%, meaning these loci behave much like they are unlinked and can assort independently in the gamete pool. Therefore you would expect measurable recombination between them and the two loci to assort independently in many offspring. In contrast, the idea that they never recombine or that they always stay together doesn’t fit how recombination works with greater separation.

Distance between two loci on the same chromosome matters for recombination. When they are far apart, crossing over during meiosis occurs frequently between them, so recombinant chromatids are produced in a substantial fraction of gametes. As this distance increases, the recombination frequency approaches 50%, meaning these loci behave much like they are unlinked and can assort independently in the gamete pool. Therefore you would expect measurable recombination between them and the two loci to assort independently in many offspring. In contrast, the idea that they never recombine or that they always stay together doesn’t fit how recombination works with greater separation.