82 What You Know So Far: Sources of Variation

Summarise what you know about this topic so far under the headings provided. You can draw diagrams or mind maps, or write short notes to organise your thoughts in preparation for the NCEA style essay question that follows. Use the points in the introduction and the hints provided to help you:

Mutation as a source of new alleles HINT: Define the term allele and explain how mutations produce new alleles.

Meiosis and variation HINT: Explain how independent assortment and crossing over during meiosis produces variation.

Monohybrid inheritance HINT: Include definitions and expected genotype and phenotype ratios for monohybrid inheritance patterns, including crosses involving codominance, incomplete dominance, and lethal alleles.

Dihybrid inheritance HINT: Explain dihybrid inheritance and explain how linkage and recombination affect variation.