Biology Exam1 chapter 11

Biology Exam1 chapter 11 - Lecture#11 Chapter 11 Gregor...

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Lecture #11: Chapter 11 Gregor Mendel published in 1866 (but no impact) Quantitative and experimental methods Garden pea: in order to study, must have: o Variation: he could pick and choose o Controlled pollinations: remove anthers -> only stigma left and then put your own pollen -> petals cover and protect it Methods: o Established true breeding lines (pure lines) o Made crosses between contrasting traits Test crosses P generation: parent -> comes from pure lines F1 generation: cross: hybrid -> F = filial (offspring) F2 generation: 3:1; 3 tall: 1 short Observations o In every case, one trait masked the expression of the other in F1 hybrid Conclusions o Genetic factors do not “blend together” in hybrids Now known as Mendel’s principle of dominance Dominant genes Recessive genes One trait masks/affects expression of the other Observation o Recessive traits reappear in F2 generation Phenotype: physical Genotype: genetic constitution Conclusion o Each characteristic governed by 2 factors – one from each parent – and these factors act like particles and separate into separate cells Mendel’s principle of segregation DIAGRAM ! – Chromosomes and Segregation Metaphase I (homologous chromosomes) (TT tt) -> Metaphase II: (TT) (tt) -> -> (T) (T) (t) (t) Modern view: o Gene locus WRONG: originally a position on a chromosome where a gene can exist Today: RIGHT: a locus is a DNA segment that governs some characteristic (such as color of pods) Each locus may have one or more specific alternatives or alleles (such as green pods) o SEE DIAGRAM ! Terminology o Genotype: homozygous dominant (BB) Phenotype: black fur o Genotype: homozygous recessive (bb) Phenotype: brown fur
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o Genotype: heterozygous (Bb) Phenotype: black fur Monohybrid cross o 2 strains with differing alleles on single locus o Punnet square o SEE NOTES FOR PUNNET SQUARE DIAGRAM S Test cross o
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