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Basic Genetics

Basic Genetics. The Father of Genetics. Gregor Mendel – Austrian monk Carried out the first studies of heredity Successfully predicted how traits would be passed Studied the garden pea plant. Basic terminology. Heredity – passing of characteristics from parents to offspring

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Basic Genetics

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  1. Basic Genetics

  2. The Father of Genetics • Gregor Mendel – Austrian monk • Carried out the first studies of heredity • Successfully predicted how traits would be passed • Studied the garden pea plant

  3. Basic terminology • Heredity – passing of characteristics from parents to offspring • Gametes –male and female sex cells • Fertilization – process where male and female sex cells unite • Produces a zygote (fertilized egg)

  4. Cross – pollination • Mendel used to fertilize pea plants • He would take pollen from one plant and dust on another

  5. Rule of unit factors • Mendel concluded that two factors control each trait • Each factor is called an allele • An allele is the different forms of a gene • Examples: blue, green, brown are different alleles for the eye color gene

  6. Rule of dominance • One allele is usually seen more often than the other • Dominant alleles are observed more often • Recessive alleles disappear • To write alleles we abbreviate: • Capitol letter for the dominant • Lower case letter for the recessive • Always use the first letter of the dominant allele for both the dominant and the recessive alleles

  7. Genotype vs. Phenotype • Phenotype: the physical appearance • Can be determined by looking at the organism • Tall, short, blue eyes, brown hair • Genotype: the allele combination • Cannot be determined by looking at the organism • Can be homozygous (TT, tt, AA, aa) • Can be heterozygous (Tt, Aa)

  8. Law of segregation • Every individual has 2 alleles of each gene and when gametes are produced, each gamete receives one of these alleles • During fertilization, gametes randomly pair to produce 4 combinations

  9. Punnett squares • Shorthand way of finding possible genotypes of the offspring • Monohybrid cross – 4 boxes in square • Dihybrid cross – 16 boxes

  10. Punnett squares • Parental gametes go along the top and down the side • Inside the boxes, the possible combinations of the offspring

  11. Dihybrid crosses • Involves two traits • Follows the law of independent assortment • Genes for different traits are inherited independently of each other

  12. Dihybrid Punnett squares • Must use all possible combinations of alleles when setting up the Punnett square • AATt x Aatt • Must use the foil method to place gametes along the top and side • Combine as usual for the combinations in the offspring

  13. Genotypic and phenotypic ratios • Once Punnett square is complete, you must calculate the genotypic ratios and the phenotypic ratios

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