What is the effect of crossing over on linkage?

• A. Crossing over increases linkage by keeping genes together
• B. Crossing over can generate new allele combinations by separating linked genes
• C. Crossing over eliminates genes
• D. Crossing over only occurs in mitosis

Answer: (B)

Crossing over happens during meiosis when homologous chromosomes pair up and exchange segments. This exchange rearranges which alleles sit together on a chromosome. If two genes are linked (located near each other on the same chromosome), crossing over between them can produce new allele combinations on the same chromosome, effectively separating the original association of those alleles. This introduces genetic diversity into gametes and reduces the strength of linkage between the genes. The result is new combinations of alleles that weren’t present in the parent, which is why the effect on linkage is to generate these novel combinations by separating linked genes. If the genes are very close, crossing over between them is rare, so linkage remains strong; if they are farther apart, recombination is more common, further breaking linkage.