Lecture 12 notes 10-17 (no slides yet)

Lecture 12 notes 10-17 (no slides yet) - o Heterozygote...

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Lecture 12 (Fitch) – 10/17/07 Phenotype – physical characteristics Character – a feature of an organism (eye color) Trait – form that character takes (blue eyes) Genotype – combination of alleles (2 gene copies) Homologous chromosomes – one from mother, one from father Sister chromatids – duplicated chromosome (during S phase) Locus – location on chromosome (genes reside here) Gene – resides on a locus Gene copy Allele – can be same (homozygous) or different (heterozygous) – can have dominance, incomplete dominance (blending effect), or co-dominance ? 3:1 phenotypic ratio comes from homozygous dominant and 2 heterozygous dominant with 1 homozygous recessive. ***Segregation between maternal and paternal copies occurs in meiosis 1*** Differences and Interactions between alleles: - Incomplete dominance o Heterozygotes are intermediate in phenotype - Codominance o Diff phenotypes expressed together (e.g. ABO, MN) - “Overdominance”
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Unformatted text preview: o Heterozygote advantage (e.g. sickle-cell anemia)-Epistasis o Alleles at one locus alter expression of alleles at another locus (e.g. albinism)-Polygenic inheritance o Additive effects of alleles at multiple loci on the same phenotype Other genetic concepts-Pleiotropy o The effect of e gene on multiple features of an organism (e.g. mutation affecting eye color and deafness in cats)-Penetrance o Probability that a phenotype will be expressed for a particular genotype (e.g. Type I diabetes in monozygotic twins)-Expressivity o The degree to which the phenotype is expressed (e.g. male tail tip lengths in lin-41 (gf) mutants of C. elegans ) The multifactorial phenotype-Phenotype also results from interaction between genotype and environment (and epigenetics – not everything you inherit is from DNA)-Ex. Soil acidity yields diff color hydrangeas, butterflies born diff colors in diff seasons....
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Lecture 12 notes 10-17 (no slides yet) - o Heterozygote...

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