What is a single base-pair site in a genome where nucleotide variation is found in at least 1% of the population called?

A single base-pair site in a genome where nucleotide variation occurs in at least 1% of the population is termed a single nucleotide polymorphism, or SNP. SNPs represent the most common form of genetic variation among individuals and are significant in various biological and medical research areas.

They can affect how individuals respond to drugs, their susceptibility to environmental factors, and the likelihood of developing certain diseases. An example would be a site in the human genome where the nucleotide adenine (A) might be present in one individual and guanine (G) in another, with this variation being observed in at least 1% of a population sample. This definition underscores the importance of SNPs in genetics, evolutionary biology, and personalized medicine.

The other concepts listed do not fit this definition. A mutation generally refers to any change in the DNA sequence, which may not necessarily be present at the frequency required to classify as a SNP. A gene locus refers to the specific physical location of a gene on a chromosome, not specifically associated with nucleotide variation at a population level. Allele frequency measures how common an allele is in a population but does not define a specific site of variation like an SNP does.