Pa help po please please ​

What word is used to describe differences of individual organisms

Natalie had random hand movements when she was two months old. when she was six months old, she used to grab a block with her whole hand. now at the age of ten months, she can grasp the same block with her thumb and forefinger. this sequence of growth in her hand and finger movements is according to the pattern.

How does the study of genetic disorders such as pku biologists understand normal alleles?