I'm pretty sure it's condensation.
Answer:
allele is the pair of gene controlling the pair of contrasting characteristics
It helps because say the hinge joint had a structure as one of a ball-and-socket joint the knee (where the hinge joint is located) wouldn't bend it would rotate/ spin like our shoulders. This is how classifying joints according to their structure and function can/ may help describe human movement.
It would have to be middle childhood
