CHAPTER 11:  MENDELIAN PATTERNS OF INHERITANCE

I. Gregor Mendel (1822-1884) father of modern genetics

            A. Austrian Monk: studied science and math

            B. he was a substitute science at the local technical high school

            C. blending: theory of his time, always produce intermediate appearance

                        1. did not account for variation or diversity

            D. his work was not recognized until 1900

            E. experimented with pea plants

                        1. easy to grow, had a short growing time, could be cross-pollinated

                        2. studied simple traits, one at a time

                        3. true-breeding, pure line: always gives the same trait when self-pollinated

                        4. kept careful records, applied mathematical principles to data

II. monohybrid cross

            A. hybrid: a product of true-breeding parents, for different forms of a single trait

            B. P generation: parents

            C. F₁ generation: first generation (all like one parent)

            D. F₂ generation: second generation (3:1 ratio)

            E. law of segregation: 2 factors for each trait, separate into different gametes

            F. alleles: alternate forms of a gene

                        1. law of dominance: dominant; trait always shows when present (T)

                        2. recessive: must have 2 genes to show this trait (t)

                        3. locus: location of alleles on a chromosome

                        4. homozygous: 2 alleles the same (dominant or recessive)

                        5. heterozygous: alleles are different

            G. genotype: genes present (TT)

            H. phenotype: physical appearance from gene expression (tall)

            I. Monohybrid cross: for one trait

                        1. Punnett square: calculate genotypes

                        2. probability: chance that an event will happen, expressed in a ratio, ex)

                            3: 1

                                    a. multiplicative law: possible combinations of 1 trait =1/2 x 1/2,EE = 1/2 x 1/2 = 1/4

                                    b. additive law: sum of probabilities of each way an event can

                                       occur, ex) unattached earlobes (EE, Ee, eE) = 1/4 + 1/4 + 1/4 = 3/4

                        3. testcross: cross against homozygous recessive to determine parents genotype

III. Dihybrid cross: 2 characteristics at once

            A. law of independent assortment: members of gene pairs separate from each

            other independently of other gene pairs; exception: (linked genes)

            B. all possible gametes (4)

            C. 16 possible choices (4²)