Concept:Genes exist in multiple variant forms called alleles, which account for inherited differences.
Explanation:Each gene can have different versions.
These versions are known as alleles.
For example, a gene for flower colour may have alleles for red or white.
Alleles can be dominant or recessive.
A dominant allele expresses its trait even in a single copy.
A recessive allele requires two copies to show the trait.
Other options are not correct.
Genotype is the complete set of genes in an organism.
Sib pairs refer to siblings used in genetic linkage studies.
Isomers are chemical compounds with the same formula but different structure.
Answer: Alleles (Option C)