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Genetics

Genetics. *transmission of traits – heredity *variation *genetics. Two main hypotheses on how traits were transmitted: *blending inheritance *particulate inheritance. The father of transmission genetics:. Gregor Johann Mendel 1822-1884. *P - parental generation.

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Genetics

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  1. Genetics *transmission of traits – heredity *variation*genetics

  2. Two main hypotheses on how traits were transmitted: *blending inheritance*particulate inheritance The father of transmission genetics: Gregor Johann Mendel 1822-1884

  3. *P - parental generation *F1 – first filial generation *F2 – second filial generation Mendel tracked heritable characters for three generations -Example: F2 P X Tall Dwarf F1 – all Tall Tall

  4. *genes and alleles Mendel’s hypotheses (to explain his results) 1. Alternative versions of genes (alleles) account for variation in inherited characters 2. For each character, an organism inherits two alleles, one from each parent

  5. 3. If two alleles differ, one is dominant, the other recessive 4. The two alleles for each character segregate (separate) during gamete production. P: X Tall Dwarf DD dd F1 – all Tall Tall Mendel’s Law of Segregation Dd

  6. D D d d Punnett Square predicts the results of a genetic cross between individuals of known genotype Tall Dwarf X P: DD dd Gamete formation: *Homozygous *Heterozygous *genotype *phenotype

  7. Mendel’s Law of Independent Assortment *What happened when he looked at two characters? If they segregate together: If they segregate independently:

  8. Example: P1 X gw yellow, round green, wrinkled gw GGWW ggww gw F1 gw All yellow, round Dihybrid cross-A genetic cross between two individuals involving two characters Punnett square and the law of independent assortment: GW GW GW GW GgWw

  9. F1 F1 X GW All yellow, round All yellow, round Gw GgWw GgWw gW gw 9:3:3:1 Phenotypic ratio; Genotypic ratio as follows: 1/16 GGWW, 2/16 GGWw, 2/16 GgWW, 4/16 GgWw F2 9/16 yellow, round 1/16 GGww, 2/16 Ggww 3/16 yellow, wrinkled 1/16 ggWw, 2/16 ggWw 3/16 green, round 1/16 ggww 1/16 green, wrinkled Punnett square and the law of independent assortment: GW Gw gW gw

  10. Mendelian inheritance is based on probability Example- coin toss *1/2 chance landing heads *Each toss is an independent event *Coin toss, just like the distribution of alleles into gametes *The rule of multiplication – determines the chance that two or more independent events will occur together ½ x ½ = ¼

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