Think and discuss: Why do you think deleterious dominant alleles are not very common?
Deleterious dominant alleles are not very common because they are more likely to be eliminated from a population through natural selection. When a deleterious dominant allele is present in an individual, it will have a harmful effect on the individual's phenotype, making it less likely to survive and reproduce. This means that individuals carrying the deleterious dominant allele are less likely to pass it on to future generations, reducing its frequency in the population over time.
Additionally, dominant alleles are more likely to be expressed in the phenotype of an individual, making the negative effects of a deleterious dominant allele more apparent and more likely to be subject to selection pressure. In contrast, recessive alleles are only expressed in the phenotype when they are present in a homozygous state, making them harder to detect and eliminate from a population.
Overall, the rarity of deleterious dominant alleles is a result of the effects of natural selection and the visibility of their harmful effects in individuals carrying them. These factors work together to reduce the frequency of deleterious dominant alleles in populations.