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Introduction to Genetics

All-Star Science. Introduction to Genetics. Father of Genetics. Gregor Mendel (1822-1884). Responsible for the Laws governing Inheritance of Traits. Gregor Johann Mendel. Austrian monk Studied the inheritance of traits in pea plants Developed the laws of inheritance

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Introduction to Genetics

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  1. All-Star Science Introduction to Genetics

  2. Father of Genetics Gregor Mendel(1822-1884) Responsible for the Laws governing Inheritance of Traits

  3. Gregor Johann Mendel • Austrian monk • Studied the inheritance of traits in pea plants • Developed the laws of inheritance • Mendel's work was not recognized until the turn of the 20th century

  4. Gregor Johann Mendel • Between 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants • He found that the plants' offspring retained traits of the parents • Called the “Father of Genetics"

  5. Site of Gregor Mendel’s experimental garden in the Czech Republic

  6. Genetic Terminology • Trait - any characteristic that can be passed from parent to offspring. • Heredity - passing of traits from parent to offspring • Genetics - study of heredity

  7. Types of Genetic Crosses • There are different types of genetic crosses. We are going to be dealing with the simplest type. • Monohybrid cross - cross involving a single traite.g. flower color

  8. Designer “Genes” • Alleles - two forms of a gene (dominant & recessive) • Dominant - stronger of two genes expressed in the hybrid; represented byacapital letter (R) • Recessive - gene that shows up less often in a cross; represented by alowercase letter (r)

  9. More Terminology • Genotype - gene combination for a trait(e.g. RR, Rr, rr) • Phenotype - the physical feature resulting from a genotype(e.g. red, white)

  10. Genotype & Phenotype in Flowers Genotype of alleles:R= red flowerr= yellow flower All genes occur in pairs, so 2alleles affect a characteristic Possible combinations are: GenotypesRRRrrr PhenotypesRED RED YELLOW

  11. Genotypes • Homozygousgenotype - gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr);also calledpure  • Heterozygousgenotype - gene combination of one dominant & one recessive allele    (e.g. Rr); also calledhybrid

  12. Punnett Square Used to help solve genetics problems

  13. Genes and Environment Determine Characteristics

  14. Monohybrid Crosses

  15. Monohybrid Cross • Trait: Seed Shape • Alleles: R – Round r – Wrinkled • Cross: RoundseedsxWrinkled seeds • RRxrr Genotype:Rr Phenotype:Round GenotypicRatio:All alike PhenotypicRatio: All alike r r Rr Rr R R Rr Rr

  16. Genetic Practice Problems

  17. Cross these two plants. t t T T • tall (TT) x dwarf (tt) pea plants

  18. Solution: t t produces the F1 generation Tt Tt T Tt Tt T All Tt = tall (heterozygous tall) tall (TT) vs. dwarf (tt) pea plants

  19. Breed the F1 generation T t T t • tall (Tt) vs. tall (Tt) pea plants

  20. Solution: T t produces the F2 generation Tt TT T 1/4 (25%) = TT 1/2 (50%) = Tt 1/4 (25%) = tt Tt tt t 1:2:1 genotype 3:1 phenotype tall (Tt) x tall (Tt) pea plants

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