Higher Dangers of a Reduced Gene Pool

Higher Dangers of a Reduced Gene Pool

Repeated selective breeding narrows the gene pool — the range of different alleles in the population decreases with each generation because only a subset of individuals are chosen to breed. This has serious consequences:

• Inbreeding depression: When closely related individuals breed, the probability of offspring inheriting two copies of the same recessive allele (becoming homozygous) increases dramatically. Many harmful alleles are recessive — when homozygous, they are expressed, causing disease, reduced fertility, or structural abnormalities.
• Increased disease vulnerability: If all individuals in a population have near-identical immune system genes, a single pathogen that overcomes the immune response of one individual can infect the entire population. A genetically diverse population will always have some individuals with resistance alleles that survive disease outbreaks.
• Reduced adaptive potential: With fewer alleles available, the population has fewer options for adaptation if the environment changes. A narrow gene pool reduces the population's ability to respond to new selection pressures.

This is why conservation programmes for endangered species carefully manage breeding to maintain as much genetic diversity as possible, even when population numbers are low.