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Chapter 12 Patterns of Inheritance

Early Ideas about Heredity . People knew that sperm and eggs transmitted information about traitsBlending theoryProblem:Would expect variation to disappearVariation in traits persists. Gregor Mendel. 1822-1884Central European monkIdeas published in 1866Unrecognized until 1900. . Mendel's

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Chapter 12 Patterns of Inheritance

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    1. Chapter 12 Patterns of Inheritance

    2. Early Ideas about Heredity People knew that sperm and eggs transmitted information about traits Blending theory Problem: Would expect variation to disappear Variation in traits persists

    3. Gregor Mendel 1822-1884 Central European monk Ideas published in 1866 Unrecognized until 1900

    4. Mendels Research Plants But mechanisms of heredity are essentially the same for all complex life forms Also apply to people and other animals

    5. Pisum sativum Common pea plant Flowers are either purple or white Flower position is axil or terminal Seed color is yellow or green Seed shape is round or wrinkled Pod shape is inflated or constricted Pod color is yellow or green Stem length is long or short

    6. Genes Units of information about specific traits Passed from parent to offspring (inherited) Has a specific location (locus) on a chromosome

    7. Diploid 2n Pairs of genes Homologous

    8. Mutations Alter gene structure May change the information about specific traits carried by the gene

    9. Allele All the different forms of the same gene are called alleles Eye color B = brown b = blue b/= green

    10. True-breeding The same allele for a trait is passed on every generation Generation 1 = aa Generation 2 = aa Generation 3 = aa Generation 4 = aa

    11. Genetic Hybrid The offspring from a cross of two different true-breeding individuals Individual 1 = aa Individual 2 = AA Offspring = Aa

    12. Names of alleles AA = homozygous (same) aa = homozygous (same) Aa = heterozygous (different)

    13. Precedence of alleles Dominant This version of the trait masks all other versions Capital letter A, R, S, H, etc.. Recessive This version of the trait is masked by the dominant trait Small case letter a, r, s, h, etc

    14. The complete allele name AA - homozygous dominant aa homozygous recessive Aa heterozygous

    15. Genotype The combination of alleles RR Rr rr AA aa Aa Etc

    16. Phenotype The trait expressed by the particular combination of alleles Tall Short Blue Brown Curly Straight Etc.

    17. Keeping track of alleles P = the parent generation F1 = the first-generation (offspring of the parents) F2 = the second-generation (offspring of the F1 generation)

    18. Monohybrid Crosses Experimental intercross between two F1 heterozygotes

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