CH11TheBasicPrinciplesofHereditypart-4

CH11TheBasicPrinciplesofHereditypart-4 - INCOMPLETE p I...

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Unformatted text preview: INCOMPLETE p I generation - heterozygote has a phenotype intermediate to the homozygotes l:1 Figure 11—18 p 252 generation Two alleles: R1 (red) and R2 (white): neither allele is completely dominant oRed flowered plants: R1 R1 -White flowered plants: R2, R2 -Pink flowered plants: R1, R2 Genotypic and phenotypic ratios in F2 are identical 1:2:1 Gametes F2 generation ABO BLOOD GROUPS: MUL'IIPLE ALLELES and CODOMINANCE In Multiple alleles there are more than 2 alleles for a given locus in a population: IA, .23, ;' TABLE 11-3 ABM Codominance — Alleles IA and IB — °Alfele i'doesn’t encode — are always expressed as recognition a recognition protein glycoproteins on red blood cells Phenotype Antigen (blood type) Genotypes on RBC A lAlA, lAi A B lBlB, is! B AB lAlB A, B 0 ii None Antibodies to A or B Antigens in Plasma Anti-B Anti~A None Anti—A, anti—B * This table and the discussion of the ABO system have been simplified somewhat. Note that the body produces antibodies against the antigens tracking on its own red blood cells (RBCs). Because oftheir specificity for the correspondng antigens, these antibodies are used in standard tests to determine blood types. 12 POLVGENIC INHERITANCE 0'0 000 MulTipIer separaTe pairs of genes have fag); X 0 O O addiTive effecTs an The same characTer Aasbcc Figure 11-22 p 256 l Normal curve - mosT of / populaTion has The inTermediaTe phenoType Polygenes in human 20 skin color - 3 loci -Dark skin alleles: A, B, C -LighT skin alleles: a, b, c _L U) Number 01 individuals (F2) Skin pigmentation NORM of REACTION: ENVIRONMENTAL IMPACT on PHENOTVPE NaTure versus nurTure: are characTerisTics influenced more by genes or by The environmenT? ° nuTriTion influences heighT °exercise alTers build ° sun—Tanning darkens The skin - experience improves performance on inTelligence TesTs IdenTical Twins separaTed aT birTh: larger man raised in nurTuring environmenT and smaller man suffered neglecT and malnuTriTion as a child ._y. . . l ._.\ "4.. — a .3 AI aha—E"... .m— Norm of ReacTion = range of phenoTypes ThaT resulT from The same genoType under differenT environmenTal condiTions 13 ...
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