Heterozygosity

Heterozygosity is the condition of carrying different alleles at a genetic locus, or a population-level measure of how often individuals or loci have that condition.

Allele: One of two or more alternative forms of a genetic sequence at a particular locus. Heterozygosity requires different alleles at the same locus.
Mendelian inheritance: The transmission of genetic variants from parents to offspring according to patterns of allele segregation. Segregation passes parental alleles that can combine into heterozygous offspring genotypes.
Observed heterozygosity: The fraction of sampled individuals that are heterozygous at a specified genetic locus or across loci. It measures heterozygosity directly in a sample of genotypes.
Genetic drift: Random changes in allele frequencies caused by sampling across generations, especially in small populations. Drift can eliminate alleles and reduce heterozygosity over generations.
Nucleotide diversity: The average number of nucleotide differences per site between pairs of DNA sequences in a population. Unlike heterozygosity, it measures sequence-level differences and can reflect variation within loci.
Genotype: The genetic constitution of an organism or cell, often described by its alleles at specified loci. A genotype records whether an individual is heterozygous or homozygous at each locus.
Meiosis: A cell division that produces reproductive cells with half the chromosome number of the parent cell. Meiosis separates alleles into gametes, shaping heterozygosity in offspring.
Expected heterozygosity: The probability that two alleles sampled from a population differ, calculated from allele frequencies. It estimates population heterozygosity from allele frequencies rather than counted genotypes.
Inbreeding depression: Reduced survival or reproduction in offspring of related individuals, often due to increased expression of harmful recessive alleles. Loss of heterozygosity can expose recessive variants associated with inbreeding depression.
Allelic richness: The number of distinct alleles observed at a genetic locus, often adjusted for sample size. It counts allele types rather than the frequency of heterozygous genotypes.

Linked from 13 pages