Heterozygote advantage. But, balancing selection is a set of mechanisms that act to maintain certain traits in a population, which is what a population needs if it wants to survive ever-changing environments. Use the example of sickle cell anemia in Nigeria to explain balancing selection.
Which of the following is the definition of a fossil cast empty molds of specimens left in sediment that are filled in with dissolved minerals Balancing selection.
would inc. and dec. until it reached equilibrium (balanced polymorphism)
Putting two alleles together in a way that it negates negative effect. When balancing selection occurs, no single allele has a distinct advantage and thus increases in frequency. Heterozygote Advantage. When balancing selection occurs, all genotypes have equal biological fitness. - hetero.
Artificial selection takes place over a relatively short time frame: natural selection reguires long time periods. Balancing selection Selection favouring heterozygotes - as give fitness advantage compared to homozygotes So balancing selection selects against homozygous - eventually leading to both alleles having the same frequency as heterozygous genotype selected for - so allele freq. Balancing selection is often portrayed as “diversifying,” meaning that there is an advantage to new alleles, as with plant self-incompatibility (S) alleles, where the frequency-dependent selective advantage of rare pollen and pistil types is well understood to maintain many alleles [6,7], or fungal incompatibility alleles [8,9], whose selective maintenance remains unclear, despite evident similarity to plant SI. Ex: the AS genotype is important because the dominant A prevents sickle-cell anemia, and the S helps prevent death by malaria. When balancing selection occurs, phenotype does not matter.
a type of selection that occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population. -it exemplifies both balancing selection and the heterozygote advantage (and pleiotropy) - (+ +) no sickle allele, susceptible to malaria - (+ -) heterozygous individuals protected from malaria (sickle cell trait - (- … individuals have greater reproductive success than homozygotes (sickle cell anemia) Frequency dependent selection… a type of balancing selection in which heterozygous individuals have greater reproductive success than homozygotes, with the result that two or more alleles for each character are maintained in a population. The mutation rate (u) is lower than expected which shows its not maintaied by mutation-selection balance CF alleles are still maintained as heterozygotes have fitness advantage over homozygotes …
- maintains stable frequencies of two or more phenotypic forms in a population.