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Biology I - GENETICS

Biology I - GENETICS. 1-12 Novak. Gregor Mendel 1822-1884. MENDEL’S PRINCIPLES. I. ALLELES. Any organism has two units of heredity (genes) for each trait in every body cell. II. SEGREGATION.

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Biology I - GENETICS

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  1. Biology I - GENETICS 1-12 Novak

  2. Gregor Mendel 1822-1884

  3. MENDEL’S PRINCIPLES

  4. I. ALLELES • Any organism has two units of heredity (genes) for each trait in every body cell

  5. II. SEGREGATION • The two units (genes) for a trait are separated in the cell; one gene is found on a chromosome while the other is located in the same place on its partner (homologous) chromosome

  6. III. DOMINANCE • A. When two genes of a trait are different in the cells of the organism, the gene that shows up is the dominant while the gene that remains hidden is the recessive • B. Combinations of the two genes (genotypes) 1. Homozygous (pure) dominant - both genes are dominant 2. Homozygous (pure) recessive - both genes are recessive 3. Heterozygous (hybrid) - one gene is dominant & the other is recessive

  7. IV. RECOMBINATION - (INDEPENDENT ASSORTMENT) • In each new generation there is a complete new rearrangement of the units of heredity (genes)

  8. Following the Generations Cross 2 Pure PlantsTT x tt Results in all HybridsTt Cross 2 Hybridsget3 Tall & 1 ShortTT, Tt, tt

  9. Generation “Gap” • Parental P1 Generation= the parental generation in a breeding experiment. • F1 generation= the first-generation offspring in a breeding experiment. (1st filial generation) • From breeding individuals from the P1 generation • F2 generation= the second-generation offspring in a breeding experiment. (2nd filial generation) • From breeding individuals from the F1 generation

  10. Mendel’s Experimental Results

  11. Thomas Hunt Morgan 1866-1945

  12. Incomplete Dominance (blending inheritance)

  13. INCOMPLETE DOMINANCE • A condition in which both alleles for a characteristic are partially expressed

  14. R R W W Incomplete Dominance • F1 hybrids have an appearance somewhat in between or a blend of the phenotypes of the two parental varieties. • Example:snapdragons (flower) • red (RR) x white (WW) • R = red flower • W = white flower

  15. R R produces the F1 generation RW RW RW RW All RW = pink (heterozygous pink) Incomplete Dominance W W

  16. Incomplete Dominance

  17. CODOMINANCE • A condition in which both alleles for a characteristic are fully expressed

  18. Codominant white and pink

  19. Codominant white and pink

  20. Homozygous Red

  21. Hereford Red

  22. Homozygous white

  23. Roan hybrid

  24. Roan hybrid

  25. Codominant cross

  26. Sex-Linked Inheritance

  27. Color Blindness

  28. normal - trichromatic color vision protanopia red-green blindness (no red cones) deutanopia red-green blindness (no green cones) tritanopia blue-yellow blindness (no blue cones) typical achromatopsia (no cones; rod monochromat) protanomaly (anomalous red cones) deutanomaly (anomalous green cones) tritanomaly (anomalous blue cones) atypical achromatopsia (low cones; cone monochromat) TYPES OF COLOR BLINDNESS

  29. Red Green Color BlindnessMale1.01%Female0.02%

  30. Sex-linked Traits • Traits (genes) located on the sex chromosomes • Sex chromosomes are X and Y • XX genotype for females • XY genotype for males • Many sex-linked traits carried on X chromosome

  31. Hemophilia

  32. Female Carriers

  33. The effects of hemophilia

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