Members of a sexually reproducing population exhibit genetic diversity due to several key processes:
-
Meiosis: During the formation of gametes (sperm and eggs), meiosis occurs. This process includes two rounds of cell division and results in cells that have half the number of chromosomes. Importantly, meiosis introduces genetic variation through two mechanisms:
- Independent Assortment: The way chromosomes are randomly distributed into gametes during meiosis leads to a mix of maternal and paternal chromosomes in each gamete.
- Crossing Over (Recombination): Homologous chromosomes can exchange genetic material during prophase I of meiosis, creating new combinations of alleles.
-
Fertilization: The random fusion of gametes from different parents contributes to genetic diversity. Since each parent produces a unique set of gametes, the offspring inherit a unique combination of alleles from both parents.
-
Mutation: Random mutations can occur in an organism's DNA. Mutations can introduce new alleles into the gene pool, further contributing to variation within a population. Although they are generally rare, they can have significant effects when combined with recombination and independent assortment.
-
Genetic Drift: In smaller populations, chance events can lead to changes in allele frequencies over generations. This random sampling effect can increase or decrease genetic variation within the population.
-
Gene Flow: The movement of individuals (and their genes) between populations can introduce new alleles and increase genetic diversity.
These mechanisms work together to create a rich tapestry of genetic variation within sexually reproducing populations, enhancing their ability to adapt to changing environments, resist diseases, and improve overall fitness.