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Genetics

Genetics . The scientific study of heredity. What is Heredity ?. The passing of traits from parents to their offspring. “Father of Genetics” (my favorite Austrian monk) He figured out how traits are passed on before we knew about DNA, or chromosomes or meiosis. 1860s: Gregor Mendel.

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Genetics

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  1. Genetics The scientific study of heredity.

  2. What is Heredity ? The passing of traits from parents to their offspring

  3. “Father of Genetics” (my favorite Austrian monk) • He figured out how traits are passed on before we knew about DNA, or chromosomes or meiosis 1860s: Gregor Mendel

  4. Why pea plants? (was it luck?) • 1. Small • 2. Easy to grow • 3. Produces large numbers of offspring • 4. Matures quickly • 5. Plants can self or cross fertilize • 6. Many varieties • 7. Each trait has two forms • Tall/short purple/white flowers • green/yellow seeds colored/white seed coat • green/yellow seed pods inflated/narrowed seed pod • wrinkled/smooth seed Mendel studied heredity with pea plants

  5. Mendel’s Experiments led him to 3 Laws of Inheritance • The Law of Dominance • The Law of Segregation • The Law of Independent Assortment

  6. Each individual has TWO factors for each trait known as alleles • Some alleles dominate over others – the dominant allele is expressed in the offspring • Homologous chromosomes-same traits -different forms The Law of Dominance: These are alleles Freckles No Freckles Dimples No dimples Tongue roller Non-roller From Dad From Mom

  7. Represented by a letter of the alphabet Capital = dominant allele A lowercase = recessive allele a • Each allele corresponds to a gene on a chromosome - the alleles represent different forms of the gene Alleles are:

  8. The two alleles for each trait separate and move into different gametes – meiosis • Since only one egg or one sperm will contribute to the new offspring, only one allele for a trait is passed on • The chance that any allele will be passed on is 50% Law of Segregation

  9. Law of Independent Assortment • the inheritance of alleles for one trait doesn’t affect the inheritance of alleles for another trait - occurs in meiosis during metaphase 1

  10. Genotype is the combination of alleles for a particular expressed with letters • Homozygous dominant: • TT - two capital letters • Heterozygous • Tt - one of each letter (big and small) • Homozygous recessive • tt - two lower case letters Genotype:

  11. Phenotype is physical expression of the genotype Genotype Phenotype TT tall plant Tt tall plant (dominant allele always is expressed over the recessive allele) tt short plant (recessive trait is expressed only if there is no dominant gene) Phenotype:

  12. What is the genotype of homozygous dominant? • RR • What is the heterozygous genotype? • Rr • What is the homozygous recessive genotype? • rr If R = red, and r = white

  13. What is the phenotype of of RR? • Red • What is the phenotype of Rr? • Red • What is the phenotype of rr? • White If R=red and r =white

  14. If two parents are crossed (TT X tt), what are the resulting offspring? You can determine phenotypes using a Punnet square. T T parent Tt Tt t Genotypes: 4 Tt Tt Tt Phenotypes: 4 Tall t This is the first or parent generation parent

  15. Now try on your paper a cross of two of the offspring from the parent generation. This is called the first generation or the F1. T t T Tt TT Tt tt t Genotypes: 1TT: 2Tt : 1tt Phenotypes: 3 Tall: 1 Short.

  16. Vocabulary Heredity Law of Dominance Law of Segregation Law of Independent Assortment Allele Genotype Phenotype

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