Final answer:
The ratio of homozygosity in human protein-coding genes varies per individual, with an average human being about 99.9% genetically similar to another. The precise measure of gene homozygosity can be studied through whole genome sequencing, with factors like population history affecting this ratio.
Step-by-step explanation:
Estimation of Gene Homozygosity in Humans
Humans are estimated to have about 20,000 to 25,000 protein-coding genes. However, a significant portion of each individual’s genome will be homozygous, meaning they have two identical alleles for a given gene, one inherited from each parent. This ratio of homozygosity varies by each individual and is influenced by factors such as population history and genetic background.
In general, humans are thought to have a relatively high level of heterozygosity, which is the presence of different alleles at a gene locus. However, research suggests that there can be substantial homozygosity across the human genome. It's challenging to give a precise number because the homozygosity ratio varies among populations and across different genomic regions. Nevertheless, a study published in the journal “Nature” suggested that the average human is about 99.9% genetically similar to any other human, indicating a certain level of gene homozygosity across the species.
Whole genome sequencing studies can offer more detailed insights into this measure within individuals or specific populations. For example, in studies of isolated populations or those with a history of inbreeding, higher rates of homozygosity can be found. This can give an indication of the average homozygosity ratio within such groups.