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Chapter 4 - BB (1)

Sickling phenomenon greatly shortens the life span of

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Unformatted text preview: nditions of low oxygen tension of 1. Sickling phenomenon greatly shortens the life span of the red 1. blood cells blood - Anemia results Anemia 2. Odd-shaped cells clump Partial or complete blocks in capillary circulation a shorter Partial life span than unaffected ones life The sickle cell allele -fairly high frequency -parts of Africa where malaria The is found is – How come? Malaria is caused by a protozoan, Plasmodium Malaria Plasmodium A microorganism will infect a cell if microorganism certain cellular proteins function optimally optimally Heterozygotes have one altered copy Heterozygotes of the gene of – they have slightly reduced protein function function – not enough to cause serious side effects enough to prevent infections Examples include – Sickle-cell anemia and malaria – Tay-Sachs disease Some proteins function as Some homodimers homodimers – Composed of two different subunits – Encoded by two alleles of the same gene A1A1 homozygotes – Make only A1A1 homodimers A2A2 homozygotes – Make only A2A2 homodimers A1A2 heterozygotes – Make A1A1 and A2A2 homodimers – AND A1A2 homodimers – For some proteins, the A1A2 homodimer For may have better functional activity may A gene, E, encodes a metabolic enzyme gene, Allele E1 encodes an enzyme that Allele E1 functions better at lower temperatures functions Allele E2 encodes an enzyme that Allele E2 functions better at higher temperatures functions E1E2 heterozygotes produce both E1E2 enzymes enzymes – an advantage under a wider temperature an range than both E1E1 and E2E2 and homozygotes homozygotes Overdominance is related to a common mating Overdominance strategy used by animal and plant breeders strategy Two different highly inbred strains are crossed – The hybrids may display traits superior to both parents – This phenomenon is termed ______________ Heterosis is used to improve...
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