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Inheritance and Evolution
Quick questions on Linkage and gene interactions: H2 Biology Inheritance and Evolution
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is recombination by crossing over?Show answer
New combinations (recombinants) arise when homologous chromosomes exchange segments during crossing over in prophase of meiosis I, at points called chiasmata. A crossover between two linked genes produces recombinant gametes. The closer the genes, the rarer the crossover between them, so the fewer the recombinants. This is the basis of gene mapping.
What is epistasis?Show answer
In epistasis, one gene affects or masks the expression of another. This produces modified ratios. For example, if both genes must have a dominant allele for a phenotype to appear, the 9:3:3:1 ratio collapses into 9:7 (the 9 with both dominant versus the 7 lacking one). Other interactions give ratios such as 12:3:1 or 9:3:4.
What is q1?Show answer
State what is meant by autosomal linkage. [1 mark]
What is q2?Show answer
Explain how recombinant gametes are produced from linked genes. [2 marks]
What is q3?Show answer
Define epistasis. [1 mark]
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