Gene s controls the sharpness of spines in a type of cactus. cacti with the dominant allele, s, have sharp spines, whereas homozygous recessive ss cacti have dull spines. at the same time, a second gene, n, determines whether or not cacti have spines. homozygous recessive nn cacti have no spines at all. the relationship between genes s and n is an example of which of the following inheritance patterns? a) incomplete dominance
b) epistasis
c) pleiotropy
d) codominance