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Mendel’s Legacy

Mendel’s Legacy

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Mendel’s Legacy

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  1. Mendel’s Legacy Genetics

  2. Gregor Mendel • Father of genetics • Researched heredity looking at traits or genetically determined variant of a characteristic. • Pea plant

  3. Mendel’s Methods • Pollination • Self-pollination occurs when pollen is transferred from the anthers of a flower to the stigma of either that flower or another flower on the same plant. • Cross-pollination occurs between flowers of two plants

  4. Monohybrid cross • Cross for only one trait • Legend: • Trait (pea plant height) • P1 – Parents • F1 – First filial (son or daughter) generation • F2 – Second filial generation

  5. Mendel’s Results

  6. Mendel’s Conclusions • Factors controlled the characteristics/ traits observed • i.e. Plant height, flower color, etc. • A pair of factors must control each trait • Dominant • The factor that is observed • Recessive • The factor that is masked by the dominant factor

  7. Law of Segregation and Law of Independent Assortment • Law of Segregation states that a pair of factors is segregated, or separated, during the formation of gametes • Law of Independent Assortment states that factors separate independently of one another during the formation of gametes.

  8. Molecular Genetics • Each organism has two factors for each trait called genes • Two alleles for shortness, two alleles for tallness • Alleles are alternative forms for genes • Alleles are found on different copies of a chromosome (one from mom, one from dad)

  9. Genotype and Phenotype • Genotype • Gene combination of an organism • Tt, RR • Phenotype • The way an organism looks • Tt – tall plant • RR – round pea

  10. Homozygous • Two alleles for the trait are the same • RR, rr • Heterozygous • Two alleles for the trait are different • Rr

  11. Probability Probability = number of times an event is expected to happen/number of times an event could happen

  12. Mendel’s Experiment F2 generation: Dominant trait (yellow seeds) = 6,022 Recessive traits (green seeds)= 2,001 Total # plants produced= 8,023 6,022/8,023=0.75 2,001/8,023=0.25 There is a 75% probability the dominant trait of yellow seeds will occur

  13. Monohybrid Cross • Only one characteristic is tracked • Genotypic ratio • Phenotypic ratio • Testcross- identify an individual of unknown genotype

  14. Punnett Square • Used to predict the probable distribution of inherited traits in the offspring

  15. Dominance • Complete dominance- one allele is completely dominant over another allele • Incomplete dominance- a phenotype in between that of the dominant and recessive traits • Codominance-both alleles for a gene are expressed in a heterozygous offspring

  16. Dihybrid Cross • Track two traits