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Interaction between natural selection and mutation
-Situation in a pop./ species where there exists ≥2 alleles of a gene, and at least 2 alleles have frequency >1%
Polymorphism
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Polymorphism is due to ______ acting on ______ caused by _____.
- natural selection,
- genetic variation,
- mutation.
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New alleles are produced by ____
mutation
However, mutation rate for any particular allele is low. Therefore, for a new allele to increase meaningfully in its frequency in a population, it has to provide a natural selective advantage
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Situation in a pop./ species where there exists ≥2 alleles of a gene, and at least 2 alleles have frequency >1%. Due to heterozygotes having fitness (higher natural selective advantage) than homozygotes
Balanced polymorphism
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Hemoglobin consists of 2 alpha & 2 beta polypeptide chains
Sickle Cell trait
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Sickle cell hemoglobin is due to _______ affecting ___ amino acid in ___ chain
- one point mutation,
- one,
- beta,
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____ is caused by a parasite transmitted between individuals by a mosquito
malaria
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_________ for sickle cell have lower rate of malarial infection compared to ________ for "normal" hemoglobin
- heterozygotes,
- homozygotes
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Why do heterozygotes for sickle cell allele have an advantage?
They have selective destruction of red blood cells.
Uninfected RBCs do not sickle; infected RBCs sickle and kill parasites
Heterozygotes can conjointly supply oxygen to tissues and suppress parasitic proliferation
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Two other types of RBC polymorphism and malaria
Thalassemia and G-6-PD
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Spread of slash-and-burn agriculture is related to natural selective advantage of sickle cell allele (Steps of the spread of malaria)
- Agricultural practices → Mosquitoes spread → Human malaria
- → Spread of sickle-cell mutation
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Interaction of natural selection & mutation means that populations may show ____ adaptations to the ______ environmental stress
(Evolutionary, different ways of solving the same problem)
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