When a population experiences a reduction of its effective size, it generally develops a heterozygosity excess at selectively neutral loci, i.e., the heterozygosity computed from a sample of genes is larger than the heterozygosity expected from the number of alleles found in the sample if the population were at …
What causes heterozygote excess?
An excess of heterozygosity is usually associated with either hybridization, such as two divergent populations coming together, heavy selection against selfing associated with inbreeding depression or a product of small effective populations size, especially in dioecious species ( Balloux 2004 , Cabrera-Toledo et al.
What increases heterozygosity?
Remember that gene diversity is composed of two elements; 1) the number of alleles and 2) the abundance (or evenness) of the alleles. Both of these would increase the expected heterozygosity.
Does genetic drift cause heterozygote excess?
In a finite population, however, random genetic drift leads to associations between alleles at a locus and between alleles of different loci. The former results in heterozygosity excess, and the latter leads to gametic LD.
What is the significance of heterozygosity?
Heterozygosity—the condition of having two different alleles at a locus—is fundamental to the study of genetic variation in populations. Indeed, Mendel’s original work was based on tracing the transmission to progeny of the two alleles present in heterozygous individuals at individual loci or combinations of loci.
What causes heterozygosity to decrease?
Genetic drift has a greater effect on smaller populations and can lead to a decrease in genetic diversity. For example, genetic drift leads to a decrease in heterozygosity, or the number of heterozygotes in a population.
What is expected heterozygosity?
Gene diversity, or expected heterozygosity (H), is a common statistic for assessing genetic variation within populations. Estimation of this statistic decreases in accuracy and precision when individuals are related or inbred, due to increased dependence among allele copies in the sample.
What are the three causes of genetic variation?
For a given population, there are three sources of variation: mutation, recombination, and immigration of genes. However, recombination by itself does not produce variation unless alleles are segregating already at different loci; otherwise there is nothing to recombine.
How can you tell if someone is inbred?
As a result, first-generation inbred individuals are more likely to show physical and health defects, including:
- Reduced fertility both in litter size and sperm viability.
- Increased genetic disorders.
- Fluctuating facial asymmetry.
- Lower birth rate.
- Higher infant mortality and child mortality.
- Smaller adult size.
What can reduce heterozygosity?
Drift will tend to reduce heterozygosity (for our purposes this equals the proportion of heterozygotes), mutation will introduce new alleles which will serve to increase heterozygosity. This provides yet another example of a “fight” between opposing evolutionary forces.
How do you prevent inbreeding?
A simple and efficient approach to reducing inbreeding in small populations with sexes of unequal census number is to impose a breeding structure where parental success is controlled in each generation.