Incomplete Dominance
INCOMPLETE DOMINANCE A form of inheritance in which heterozygotes have a phenotype that is intermediate between homozygous dominant and homozygous recessive.
A woman has straight hair, a man has curly hair. What hair texture will their children have?
ANSWER: Their children will all have an intermediate hair texture: wavy hair. Like flower color in some plants, where for example red-flowering plants mated with white-flowering plants produce plants with pink flowers, hair texture is an example of incomplete dominance, a form of inheritance in which heterozygotes have a phenotype intermediate between homozygous dominant and homozygous recessive.
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There are two versions of the gene that specify hair texture: straight (h) and curly (H). People with straight hair are homozygous recessive (hh); they don’t produce any of the protein that causes hair to curl. People who are homozygous dominant (HH) express a full amount of hair curl protein and consequently have curly hair. Heterozygotes (Hh) express half the amount of curl protein relative to someone with curly hair, which makes their hair wavy (INFOGRAPHIC 12.6).
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In incomplete dominance, heterozygotes display a phenotype intermediate between homozygous dominant and homozygous recessive. Hair texture is an example. There are two alleles of a gene that determine the texture of hair. One allele (H) results in curly hair, and one allele (h) results in straight hair.
