Final answer:
Homologous recombination usually leads to crossovers during prophase I of meiosis, through the exchange of genetic material between non-sister chromatids of homologous chromosomes. This process results in recombinant chromosomes, increasing genetic diversity.
Step-by-step explanation:
Homologous recombination is a biological process that primarily occurs during meiosis, specifically in prophase I. During this phase, homologous chromosomes pair up and form a tetrad, which consists of four chromatids. This pairing allows for the possibility of crossover, the exchange of genetic material between non-sister chromatids of homologous chromosomes.
Crossing-over results in novel combinations of genetic material, as segments from one chromatid break off and reattach to the corresponding position on a homologous chromosome. Such recombination events between genes A and B tend to be more frequent than between genes B and C, especially if genes A and B are farther apart on the chromosome. The exchange of alleles during crossing-over is a necessary step for creating genetic diversity within a species, ensuring that offspring have unique combinations of genes inherited from their parents.
In summary, the statement that homologous recombination usually leads to crossovers is true. It requires alignment and DNA breakage of homologous chromosomes during meiosis, leading to the exchange of alleles and formation of recombinant DNA molecules. This process contributes significantly to the genetic variation observed in populations.