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Mendel and Heredity

Mendel and Heredity. Ch 11.1-3 - Genetics. Genetics. Study of Heredity Passing of traits from parents to offspring Trait : a specific characteristic. Gregor Mendel. Father of genetics Parents were farmers He became ordained as a priest Studied science & math at Univ of Vienna.

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Mendel and Heredity

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  1. Mendel and Heredity Ch 11.1-3 - Genetics

  2. Genetics • Study of Heredity • Passing of traits from parents to offspring • Trait: a specific characteristic

  3. Gregor Mendel • Father of genetics • Parents were farmers • He became ordained as a priest • Studied science & math at Univ of Vienna

  4. Mendel’s Experiments • Chose Pea plants as exp. Subjects • Easy to cross • Grow quickly • Produce high number offspring • Showed variety of contrasting traits • Purple vs white flowers • Tall vs short stems • Round vs wrinkled seeds

  5. Mendel’s experiments cont. • Chose true breeding lines of each plant/trait he studied. • True breeding always produced offspring of the same type • Crossed a true breeding plant with a plant of the opposite trait. (purple x white) • Called this the Parental (P) generation

  6. Recorded data on the offspring of this cross. (hybrid) • First Filial generation (F1) • Self pollinated the F1 offspring • Recorded data on the offspring of the 2nd generation. • Second Filial generation (F2)

  7. Analysis: F1 Generation • Always displayed one trait (he later called this the dominant trait) • Must have within it the trait from the original parents – the white trait

  8. Analysis: F2 Generation • Displayed the hidden trait, ¼ of the F2 gen. had it (he later called this hidden trait the recessive trait) • Each individual has 2 ”factors” that determine what external appearance the offspring will have • These factors are now called genes or alleles

  9. Mendel established 3 principles or laws from his research

  10. The Principle of Dominance and Recessiveness One trait is masked or covered up by another trait

  11. Principle of Segregation The 2 factors (alleles) for a trait separate during gamete formation

  12. Principle of Independent Assortment Factors of a trait separate independently of one another during gamete formation.

  13. Example: • Whether a flower is purple has nothing to do with the length of the plants stems – each trait is independently inherited.

  14. Modern Genetics • Mendel’s factors are now called Alleles. (different versions of a gene) • For every trait a person has, 2 alleles determine how that trait is expressed

  15. We use letters to denote alleles, since every gene has 2 alleles, all genes can be represented by a pair of letters PP = purple, Pp = purple pp = white

  16. Terms to know: • Homozygous: When the alleles are the same. (true breeding) Ex. AA, bb, EE, dd

  17. Terms to know: • Heterozygous: When the alleles are different. (dominant allele is expressed) Ex. Pp, Aa, Bb

  18. Terms to know: • Genotype: Letters used to denote alleles (BB, Pp, aa)

  19. Terms to know: • Phenotype: What an organism looks like. (brown,purple,curly hair….)

  20. Terms to know: • Monohybrid cross: a cross involving one pair of contrasting traits. Ex. Pp x Pp

  21. Terms to know: • Punnett Square: Used to determine the Probability of having a certain type of offspring given the alleles of the parents.

  22. How to solve a Punnett Square: • Determine the genotypes (letters) of the parents. • (AA x aa ) or (Rr x Rr) • Set up the punnett square w/one parent on each side. • Fill out the punnett square middle. • Analyze the number of offspring of each type.

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