Incomplete Dominance
Like we previously learned on codominance, we know that things in genetics aren't always so clear-cut & "simple," like Mendelian Genetics was.
Incomplete dominance is a lot like codominance, except that it is a heterozygous genotype that creates an intermediate phenotype. Unlike codominance, where the traits are independently expressed together, incomplete dominance means that they will be blended together. An individual that is incomplete dominance will have, for example, either black fur, white fur, or grey fur. This is because in incomplete dominance, the genes combine together, forming a different phenotype, instead of having both like in codominance. Mixing paint is like incomplete dominance, only it isn't genes. For example, blue & red make purple or red & white make pink. |
Here is an example of Incomplete Dominance:
If tail length in cats is an incompletely dominant trait, what would be the resulting offspring of a cross with long-tailed (HH) cats and short-tailed cats (hh)? In this case, we don't have to worry about dominant and recessive because the problems gives us the answer to that. So, we know that long-tailed cats are homozygous dominant and short-tailed cats are homozygous recessive. Now, we need to put this information into a punnett square to find the possible outcomes of color for the offspring. After that, we need to write the ratios, in this case, we know that the possible genotypes are HH, hh, or Hh and the possible phenotypes are short-tailed cats, long-tailed cats, or medium-tailed cats. Based on the punnett square, we know that the genotype, Hh, is 100%, therefore the phenotype is 100% medium length tails for the offspring of the two cats.
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