Chat with AIExam 4: Genes and Their Evolution: Population Genetics
Why is the incidence of sickle-cell anemia an excellent example of a "balanced polymorphism," in which two or more alleles are maintained by natural selection in a population?
(74) 
VerifiedHomozygous normal individuals have healthy red blood cells (and hence normal oxygen distribution to tissues)but are susceptible to malaria.Homozygous abnormal individuals display sickle-cell anemia,a very serious disease that usually results in death before reproductive age.Those who are heterozygous are more fit in malarial environments,because they display only very mild symptoms of sickle-cell anemia (if any)and are much less susceptible to malaria.Hence the sickle-cell allele is maintained in fairly high frequencies in regions where malaria is common.There is a tradeoff between a positive effect and a negative effect,so a trait that from one point of view should be selected against is maintained because,from a different point of view,it is also selected for.
What is a reproductive population,and what is its importance in the study of evolution,from the point of view of physical anthropology? How is this concept operationalized in the study of fossil species?
(63) VerifiedThe reproductive population is the minimal group of individuals that define a species,but a species may actually include multiple such groups at any moment in time.The terms breeding population,reproductive population,and deme all refer to groups of individuals of the same species that have the potential to interbreed and reproduce.The student may use the term deme,which refers to a local population that interbreeds.
Reproductive isolation is a key mechanism leading to the evolution of new species.Groups of individuals that cannot breed are said to be reproductively isolated,because something interferes with their ability to have offspring,such as the genes in the two groups being too different.This isolation can arise as a result of geographic isolation in which two or more groups are separated by a geographical feature or by distance,evolve independently,and can eventually become too different to allow interbreeding.This can lead to the rise of new species.
It is not possible to definitively define reproductive or breeding populations just from fossils.When fossils show clear difference in morphology they may represent individuals of different species. Fossils found far apart from each other are more likely to be from different species,or at least,different reproductive populations.When fossils are found geographically close to each other,and closely resemble each other,we often assume they are of the same species.
Why are frameshift mutations more likely to have an impact at the phenotypic level?
(82) VerifiedC
What is the evolution of the modern horse with a single hoof on each limb from a dog-sized ancestral species with multiple digits an example of?
(70) In certain species of nonhuman primates there are groups where only one dominant female has access to mates.The other females must wait until the opportunity to mate presents itself.This will have direct impact on "fitness," influencing which of the following?
(81) What is a point mutation that does NOT result in a change to the amino acid for which it is coded?
(81) What is the cause of the significant difference between the ABO and MN blood-type frequencies of the Dunkers and those of current American and German populations?
(74) Mutations in DNA found in which cells are most likely to have significant evolutionary consequences?
(67) You are reading a scientific article about cheetahs that have stripes down their backs instead of spots.The article refers to this as a genetic mutation.Though they have no negative impact on the cheetahs' fitness,why are the stripes nevertheless considered a genetic mutation?
(75) A study of Galápagos finches after a long period of drought found that all species of finch on one of the islands had wide beaks well adapted to break open seeds.The type of evolution that leads to this phenotype distribution is ________ selection.
(66) What is the mutation known as trisomy 21,in which an extra copy of chromosome 21 is present,more commonly known as?
(95) A genetic study conducted over two generations found that the frequencies of genotypes in the first generation were AA: 0.36,Aa: 0.48,aa: 0.16.In the second generation,genotype frequencies remained the same.According to Hardy-Weinberg equilibrium,what can we assume?
(86) Some genetic disorders decrease susceptibility to malaria.What is an example of a genetic disorder that has this effect?
(66) What effect does natural selection have on population variation?
(81) What are all of the alleles contained within a group of interbreeding individuals together known as?
(71) What type of animal does the best-documented case of industrial melanism involve?
(86) How do we know that Upper Paleolithic food foragers in Europe are ancestors to modern European populations?
(77) An individual who displays the disease sickle-cell anemia must have inherited the deleterious allele from both phenotypically normal parents.What,therefore,is this individual?
(83) 
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