If Huntington's disease is due to a dominant trait, shouldn't three-fourths of the population have Huntington's while one-fourth
has the normal phenotype? In large populations, Mendelian ratios are ineffective. Appearance of a trait in a population does not solely depend on its dominant or recessive nature. Natural selection is eliminating Huntington’s disease.
Appearance of a trait in a population does not solely depend on its dominant or recessive nature.
Explanation:
The appearance of a trait in a population is not only dependent on its dominant or recessive nature.
Huntington's disease is caused by a mutation in the gene that encodes a protein called huntingtin (Htt). This mutation produces an altered form of the Htt protein, which causes the death of nerve cells (neurons) in certain brain regions. Even if caused by a dominant gene, Huntington's disease will only be expressed in 50% of people who inherit this gene from their parents. This will depend on the organism's gene expression and other factors besides the dominant character of this gene.
