What do you call a variant form of a gene?

A variant form of a gene is referred to as an allele. Alleles are different versions of the same gene that can result in variations in traits manifested in organisms. Each individual typically has two alleles for a specific gene, one inherited from each parent, which contributes to the genetic diversity seen within a population.

Understanding alleles is fundamental in genetics because they help explain how traits are passed from parents to offspring and how variations arise within a species. For example, in the case of a gene controlling flower color, one allele may lead to red flowers while another may result in white flowers.

The other terms refer to different concepts in genetics. A trait is the observable characteristic that results from the interaction of alleles, a chromatid is one half of a duplicated chromosome involved in cell division, and a segment could refer to a portion of genetic material but does not specifically denote a variant form of a gene.