Gene s controls the sharpness of spines in a type of cactus. cactuses with the dominant allele. s, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. at the same time, a second gene, n, determines whether or not cactuses have spines. homozygous recessive nn cactuses have no spines at all the relationship between genes s and n is an example of

The connection between genes s and n is an example of epistasis. This is the occurrence where the result of one gene (locus) is reliant on the existence of one or more 'modifier genes'. In other words, it is the genetic upbringing. Initially the word meant that the phenotypic result of one gene is concealed by a different gene (locus).

they are known to reach a speed of 21 miles per hour

the answer is trees if i'm not mistaken