What is Overdominant selection?
Overdominance is a condition in genetics where the phenotype of the heterozygote lies outside the phenotypical range of both homozygous parents. Overdominance can also be described as heterozygote advantage, wherein heterozygous individuals have a higher fitness than homozygous individuals.
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Does overdominance increase genetic variation?
This situation, known as heterosis or overdominance, leads to the stable coexistence of both alleles in the population and hence contributes to the widespread genetic variation found in populations of most organisms.
What is overdominance and example?
In overdominance, the heterozygote produced by two homozygote parents shows a phenotype that is more pronounced than that of the parents. Overdominance may also mean that the heterozygote has a higher fitness relative to the counterpart homozygotes. An example of this is a heterozygote for sickle cell anemia.
Why does overdominance happen?
Overdominance. Overdominance occurs when fitness of the heterozygote is superior to that of either homozygote. The result is that both alleles are maintained in the population at an equilibrium frequency ( , read “q hat”, where q = 0) that maximizes fitness.
What is overdominance and Underdominance?
Underdominance is the case where heterozygotes are less fit than homozygotes: for two alleles A and B at a given locus, both AA and BB individuals are more fit than AB heterozygotes. This is the opposite of overdominance, a form of balancing selection, where heterozygotes have a higher fitness than both homozygotes.
What type of gene interaction is involved in sickle cell anemia?
This condition is caused by genetic changes in the HBB gene and is inherited in an autosomal recessive pattern.
How does overdominance maintain genetic diversity?
One of the classic ways to maintain genetic variation with a population is “overdominance,” in short, a state where heterozygotes exhibit greater fitness than the homozygote genotypes.
Is Sickle Cell Anemia overdominance?
Perhaps the most widely discussed example of single-gene overdominance is that of human sickle cell anemia. A hemoglobin mutation negatively affects human survival by causing sickle cell anemia, but positively affects human survival by protecting against malaria (Pauling et al.
What happens in Underdominance?
In genetics, underdominance (referred to in some texts as “negative overdominance”) is the opposite of overdominance. It is the selection against the heterozygote, causing disruptive selection and divergent genotypes.
What is the point mutation in sickle cell?
Sickle-cell anemia is caused by a point mutation in the β-globin chain of hemoglobin, causing the hydrophilic amino acid glutamic acid to be replaced with the hydrophobic amino acid valine at the sixth position. The β-globin gene is found on the short arm of chromosome 11.
Is sickle cell anemia a deletion mutation?
Sickle-cell anemia results from an A leads to T transversion in the second nucleotide of codon 6 of the beta-globin gene. We now report an uncommon beta-thalassemia gene that contains a deletion of this nucleotide.
What is Underdominance in evolution?
What type of gene mutation causes sickle-cell anemia?
Sickle cell disease (SCD) is a genetic disorder caused by a mutation in both copies of a person’s HBB gene. This gene encodes a component of hemoglobin, the oxygen-carrying protein in red blood cells.
What type of mutation is the sickle cell mutation?
As mentioned, sickle-cell anemia is the result of a change in a single nucleotide, and it represents just one class of mutations called point mutations. Changes in the DNA sequence can also occur at the level of the chromosome, in which large segments of chromosomes are altered.
What type of mutation is sickle cell?
What type of mutation causes sickle cell?
Mutations in the HBB gene cause sickle cell disease. The HBB gene provides instructions for making one part of hemoglobin. Hemoglobin consists of four protein subunits, typically, two subunits called alpha-globin and two subunits called beta-globin. The HBB gene provides instructions for making beta-globin.
Can two O positive parents have AB positive child?
But it is technically possible for two O-type parents to have a child with A or B blood, and maybe even AB (although this is even more unlikely). In fact, a child can get almost any kind of blood type if you consider the rule-breaking exceptions.