Here are some other less common synonyms:
* Alternative form of a gene
* Genetic variant
* Genotype (though this is more broadly used to describe the combination of alleles an individual carries)
It's important to note that these synonyms may not be entirely interchangeable, as they can have slightly different connotations. For example, "allele" is often used to refer to a specific version of a gene, while "gene variant" can be used more broadly to encompass any difference in a gene sequence.