Sources of Variation

Rucete ✏ Biology In a Nutshell

1. Mutation

• Mutations are the original source of genetic variation.
• They introduce new alleles into a gene pool, creating raw material for evolution.

2. Sexual Reproduction

• Increases variation by recombining alleles from both parents.
• Includes mechanisms such as:
  • Crossing over during meiosis
  • Independent assortment of homologous chromosomes
  • Random fertilization (joining of gametes)

3. Diploidy

• Diploid organisms carry two copies of each gene (2n).
• This allows recessive alleles to be preserved in heterozygotes, maintaining genetic diversity.

4. Outbreeding

• Reproduction between unrelated individuals.
• Increases genetic diversity and reduces the risk of harmful recessive traits expressing due to inbreeding.

5. Balanced Polymorphism

• Occurs when multiple alleles are actively maintained in a population.
• Can happen through:
  • Heterozygote advantage (e.g., sickle-cell trait in malaria regions)
  • Frequency-dependent selection, where the fitness of a phenotype depends on how common it is