Final answer:
The concept of incomplete dominance in genetics explains why a child may have an intermediate phenotype, such as wavy hair, when their parents have differing traits, such as one parent with one with straight hair and the other with curly hair. In the context of the hair phenotype, the genotype for straight hair would be IS-IS.
Step-by-step explanation:
Inheritance in humans can follow various patterns. One of these patterns is incomplete dominance, where a gene from each parent combines to produce an intermediate phenotype in the offspring. For instance, if one parent has an allele for curly hair (IC), and the other has an allele for straight hair (IS), their offspring will have wavy hair, an intermediate phenotype.
In the context of genetics, the genotype denotes the set of genes responsible for a particular trait. Incomplete dominance breaks from the conventional notion of dominance, where one trait completely masks the other, offering instead a middle-ground expression of the two traits being considered.
In the example given (curly, wavy, straight hair inheritance), the genotype for straight hair would be IS-IS. This is because the IC allele for curly hair is incompletely dominant over the IS allele for straight hair, and thus the IS-IS genotype would result in a straight hair phenotype.
Learn more about Incomplete Dominance