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Mendel and Genetics

Mendel and Genetics. Mrs. Potz. Gregor Mendel. Carried out the first important studies of heredity. Passing on of characteristics from parents to offspring Genetics Branch of biology that studies heredity Studies inheritance pattern of traits Characteristics that are inherited.

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Mendel and Genetics

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  1. Mendel and Genetics Mrs. Potz

  2. Gregor Mendel • Carried out the first important studies of heredity. • Passing on of characteristics from parents to offspring • Genetics • Branch of biology that studies heredity • Studies inheritance pattern of traits • Characteristics that are inherited

  3. Mendel’s experiment • Used pea plants • Reproduce sexually • Have two distinct sex cells • Gametes are sex cells • Male and female gametes are in the same flower • Pollination and fertilization occur in the same flower • Pollination: transfer of male pollen grains to the pistil of a flower • Fertilization: male gamete in the pollen grain meets and fuses with the female gamete in the ovule

  4. Careful researcher • Studied one trait at a time • Analyzed data mathematically

  5. Monohybrid crosses • Performed controlled crosses • Crossed tall and short pea plants • Created hybrids • Offspring that have different forms of a trait • Two parent plants differed by a single trait: height

  6. First Generation • Crossed tall with short pea plants • All offspring were tall • F1 generation

  7. Second Generation • First generation allowed to self-pollinate • ¾ of offspring were tall • ¼ of offspring were short • Ratio 3:1 • F2 generation

  8. Unit Factors • Mendel’s conclusion • Unit factors control each trait • Alleles: alternative forms of a gene • One from mother and one from father

  9. Rule of Dominance • Dominant trait: the observed trait • Uses an uppercase letter • Recessive trait: the trait that disappears • Uses a lowercase letter

  10. Law of Segregation • Mendel’s 1st law of heredity • Two alleles for each trait must combine when gametes are formed. • A parent passes only one allele for each trait to offspring

  11. Phenotypes and Genotypes • Phenotype • The way an organism looks and behaves • Genotype • The gene combination an organism contains • Homozygous (TT or tt) • Two alleles for the trait are the same • Heterozygous (Tt) • Two alleles for the trait differ from each other

  12. Dihybrid Crosses • Organisms differ from each other in two traits rather than one • F1 generation: all traits were dominant • Yellow color (Y) • Round shape (R) • F2 generation • RRYY: round yellow • RRyy: round green • rrYY: wrinkled yellow • rryy: wrinkled green

  13. Law of Independent Assortment • Genes for different traits are inherited independently of each other • When a pea plant with the genotype RrYy produces gametes, the alleles R and r will separate from each other (law of segregation) as well as from the alleles Y and y (law of independent assortment). • Alleles recombine in four different ways.

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