What happens to the frequency of a recessive allele when selection is against the recessive phenotype?
Because of the sheltering effect of heterozygotes, selection against recessive phenotypes changes the frequency of the recessive allele slowly. Therefore, to halve an allele frequency from 1/50 to 1/100 would proceed slowly from 1/50 to 1/51, 1/52, 1/53, and so on and would take 50 generations to get to 1/100.
How does fitness affect allele frequency?
Natural selection can cause microevolution, or a change in allele frequencies over time, with fitness-increasing alleles becoming more common in the population over generations. Disruptive selection: Both extreme phenotypes have a higher fitness than intermediate phenotypes.
Would selection against a dominant allele or a recessive allele show a greater change in allele frequency over a few generations?
Since natural selection favors genotypes that are better able to survive and reproduce, a new “favored” (i.e., beneficial) allele will increase in frequency over a number of generations. The rate of increase in frequency of the favored allele will depend on whether the allele is dominant or recessive.
Why is it hard for selection to remove recessive alleles from the population even if they reduce an individual’s fitness?
It is almost impossible to totally eliminate recessive alleles from a population, because if the dominant phenotype is what is selected for, both AA and Aa individuals have that phenotype. Individuals with normal phenotypes but disease-causing recessive alleles are called carriers.
Are dominant alleles better than recessive?
When an allele is dominant, the characteristic it is connected to will be expressed in an individual. When an allele is recessive, the characteristic it is connected to is less likely to be expressed.
Are recessive alleles rare?
Recessive disorders are often rare, with very few people affected within one family.To show a recessive disease , you need two mutant copies of a gene (alleles). Both parents are carriers – one normal allele and one disease allele. Not all recessive alleles cause disease.
What is the rarest combination of hair and eye color?
The title of rarest hair color/eye color combination belongs to red-haired folks with blue eyes. According to Medical Daily, both blue eyes and red hair are recessive traits, so the likelihood of both traits appearing together is actually pretty slim.