Answer: alleles
Step-by-step explanation:
Alleles are different forms of a given gene. Alleles are mutated forms of a given gene which controls a particular trait. For instance, the gene that codes for hemoglobin is denoted with the letter A but the gene has another variant denoted by S. In abnormal hemoglobin S (sickle hemoglobin), glutamate is replaced by valine at position 6 in the amino acid sequence of the two beta chains of hemoglobin. This change in the amino acid sequence causes the red blood cells to have a sickle shape resulting in sickle cell disease. Therefore hemoglobin A and S are alleles of a given gene.