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History of Genetics

History of Genetics. Biology. Genetics. How characteristics are transmitted from parents to offspring. Gregor Mendel. Gregor Mendel (1822-1884). worked with Pisum satium (pea plant). Mendel studied 7 characteristics. Flower color

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History of Genetics

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  1. History of Genetics Biology

  2. Genetics • How characteristics are transmitted from parents to offspring

  3. Gregor Mendel

  4. Gregor Mendel (1822-1884) • worked with Pisum satium (pea plant)

  5. Mendel studied 7 characteristics • Flower color • Flower position along stem • Seed color • Seed shape • Pod shape • Pod color • Stem length

  6. Mendel’s Experiments • Mendel’s First Cross • Crossed “purebred” purple • with “purebred” white • + P (parent) generation • - F1 – purple • Crossed F1 hybrids • + produced F2 generation • - 3 purple : 1 white

  7. Mendel’s Ideas of Inheritance • Alternative versions of genes (alleles) account for variations in inherited characters. • + each gene resides at a particular location of a chromosome and can exist in variable forms (two different forms for flower color) P Pp p

  8. Mendel’s Ideas of Inheritance • For each characteristic, an organism inherits two alleles, • one from each parent. • + an organism is either homozygous (two of the same alleles) or heterozygous (two different alleles) Homozygous Heterozygous

  9. Mendel’s Ideas of Inheritance • If the two alleles differ, the dominant allele is fully expressed and the recessive allele has no noticeable affect on appearance. • + heterozygotes express the dominant trait RR rr Rr

  10. Mendel’s Law of Segregation • The two alleles for each character segregate during • gamete production. • + ovum/sperm get only one of the two alleles (haploid)

  11. P generation Phenotype: Purple/White Genotype: PP/pp F1 generation Phenotype: Purple Genotype: Pp F2 generation? Genotype/Phenotype can be predicted using a Punnet Square

  12. Mendel’s Law of Independent Assortment Each pair of alleles segregates into gametes independently. WH wh Wh wH

  13. Mendel’s Law of Independent Assortment Parental Genotypes GGWW ggww gw GW Parental Gametes? GgWw F1 Genotypes? gw GW Gw gW F1 Gametes?

  14. Beyond Mendel... Different Types of Inheritance:

  15. Complete Dominance Incomplete Dominance Mendel’s Traits Snapdragon Color

  16. Incomplete Dominance One allele does not dominant the other in the heterozygous condition. Both alleles are expressed but a new phenotype appears that is intermediate. RR Rr rr

  17. Codominance Both alleles in the Heterozygous condition are dominant. CC Cc cc

  18. Codominance & Multiple Alleles

  19. Incomplete Dominance

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