HETEROZYGOSTIY (Ho) VS COI
The coefficient of inbreeding and heterozygosity are often confused.
The Coefficient of Inbreeding (COI) is the probability that both alleles at a locus are identical by descent (IBD). It can be estimated either from pedigree data or DNA. Because it is a probability, values range from 0 to 1 (or 0% to 100%). From DNA, it is usually measured by quantifying the fraction of the genome that is homozygous using "runs of homozygosity" (ROH). Because it is a probability, it reflects "expected" (theoretical) inbreeding.
A statistic called Observed Heterozygosity (Ho; or just heterozygosity as here) is the observed proportion of loci that are heterozygous (two different alleles). It reflecs the allelic diversity at loci, and because it is a proportion (# heterozygous SNPs/ total # SNPs). values range from 0 to 1. This is an actual measure of allelic diversity, not a probability.
It is determined from SNP ("snip") genotyping of DNA; it cannot be estimated from pedigrees. Ho reflects actual fraction of heterozygous loci of the total number of SNPs assessed.
The Coefficient of Inbreeding (COI) is the probability that both alleles at a locus are identical by descent (IBD). It can be estimated either from pedigree data or DNA. Because it is a probability, values range from 0 to 1 (or 0% to 100%). From DNA, it is usually measured by quantifying the fraction of the genome that is homozygous using "runs of homozygosity" (ROH). Because it is a probability, it reflects "expected" (theoretical) inbreeding.
A statistic called Observed Heterozygosity (Ho; or just heterozygosity as here) is the observed proportion of loci that are heterozygous (two different alleles). It reflecs the allelic diversity at loci, and because it is a proportion (# heterozygous SNPs/ total # SNPs). values range from 0 to 1. This is an actual measure of allelic diversity, not a probability.
It is determined from SNP ("snip") genotyping of DNA; it cannot be estimated from pedigrees. Ho reflects actual fraction of heterozygous loci of the total number of SNPs assessed.
COI and heterozygosity are related, but the are not the same and the relationship between them is not simple. A dog with a low COI can still have low heterozygosity if the breed is inbred. However, loss of genetic diversity affects heterozygosity even if COI is low.
This graph was created from average values of heterozygosity and inbreeding by breed from two different studies, where each point represents a breed. If you are trying to manage inbreeding, this graphs indicates that an average COI of 0.1 (10%) roughly corresponds to heterozygosity of about 0.42.
