Which event during meiosis generates genetic variation among gametes?

(1) Crossover between homologous chromosomes

(2) Random assortment of homologous chromosomes at the first meiotic division

Explanation

Two events during meiosis generate genetic variation:

• Crossover - physical exchange of chromosome segments between homologous pairs creates new allele combinations
• Random (independent) assortment - the orientation of each homologous pair at the cell equator during the first division is random, so each gamete receives a different mix of maternal and paternal chromosomes

DNA replication and spindle formation are necessary for division but do not themselves generate variation.