11 3 Exploring Mendelian Genetics 11 3 Exploring

11– 3 Exploring Mendelian Genetics 11 -3 Exploring Mendelian Genetics Slide 1 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Independent Assortment To determine if the segregation of one pair of alleles affects the segregation of another pair of alleles, Mendel performed a twofactor cross. Slide 2 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Independent Assortment The Two-Factor Cross: F 1 Mendel crossed true-breeding plants that produced round yellow peas (genotype RRYY) with true-breeding plants that produced wrinkled green peas (genotype rryy). RRYY x rryy All of the F 1 offspring produced round yellow peas (Rr. Yy). Copyright Pearson Prentice Hall Slide 3 of 31 End Show

11– 3 Exploring Mendelian Genetics Independent Assortment The alleles for round (R) and yellow (Y) are dominant over the alleles for wrinkled (r) and green (y). Slide 4 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Independent Assortment The Two-Factor Cross: F 2 Mendel crossed the heterozygous F 1 plants (Rr. Yy) with each other to determine if the alleles would segregate from each other in the F 2 generation. Rr. Yy × Rr. Yy Slide 5 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Independent Assortment The Punnett square predicts a 9 : 3 : 1 ratio in the F 2 generation. Slide 6 of 31 End Show

11– 3 Exploring Mendelian Genetics Independent Assortment The alleles for seed shape grouped themselves without affecting seed color. This principle is known as independent assortment. Genes that segregate independently do not influence each other's inheritance. Slide 7 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Independent Assortment The principle of independent assortment: genes for different traits can segregate independently during the formation of gametes. Independent assortment helps account for the many genetic variations observed in plants, animals, and other organisms. Copyright Pearson Prentice Hall Slide 8 of 31 End Show

11– 3 Exploring Mendelian Genetics A Summary of Mendel's Principles • Genes are passed from parents to their offspring. • If two or more forms (alleles) of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive. Slide 9 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics A Summary of Mendel's Principles • In most sexually reproducing organisms, each adult has two copies of each gene. These genes are segregated from each other when gametes are formed. • The alleles for different genes usually segregate independently of one another. Slide 10 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Beyond Dominant and Recessive Alleles Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes. Slide 11 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Beyond Dominant and Recessive Alleles Incomplete Dominance Incomplete dominance: One allele is not completely dominant over another. In incomplete dominance, the heterozygous phenotype is between the two homozygous phenotypes. Slide 12 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Beyond Dominant and Recessive Alleles RR A cross between red (RR) and white (WW) four o’clock plants produces pinkcolored flowers (RW). WW Slide 13 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Beyond Dominant and Recessive Alleles Codominance Both alleles contribute to phenotype. In certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers. Heterozygous chickens are speckled with both black and white feathers. The black and white colors do not blend to form a new color, but appear separately. Slide 14 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Beyond Dominant and Recessive Alleles Multiple Alleles: Genes that are controlled by more than two alleles. More than two possible alleles can exist in a population. Each individual can’t have more than two. A rabbit's coat color is determined by a single gene that has at least four different alleles. Slide 15 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Beyond Dominant and Recessive Alleles Different combinations of alleles result in the colors shown here. KEY C= full color; dominant to all other alleles cch = chinchilla; partial defect in pigmentation; dominant to ch and c alleles ch = Himalayan; color in certain parts of the body; dominant to c allele chhc h, cch ch hh chc AIbino: cc Chinchilla: c Himalayan: c c, or c c, or c Full color: CC, Cc , or Cc Copyright Pearson Prentice Hall c = albino; no color; recessive to all other alleles Slide 16 of 31 End Show

11– 3 Exploring Mendelian Genetics Slide 17 of 31 End Show

11– 3 Exploring Mendelian Genetics Beyond Dominant and Recessive Alleles Polygenic Traits: Traits controlled by two or more genes. Skin color in humans is a polygenic trait controlled by more than four different genes. Slide 18 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Exploring Mendelian Genetics Applying Mendel's Principles Thomas Hunt Morgan used fruit flies to advance the study of genetics. Morgan and others tested Mendel’s principles and learned that they applied to other organisms as well as plants. Slide 19 of 31 Copyright Pearson Prentice Hall End Show

11– 3 Click to Launch: Continue to: - or - Slide 20 of 31 End Show Copyright Pearson Prentice Hall

11– 3 In a cross involving two pea plant traits, observation of a 9 : 3 : 1 ratio in the F 2 generation is evidence for a. the two traits being inherited together. b. an outcome that depends on the sex of the parent plants. c. the two traits being inherited independently of each other. d. multiple genes being responsible for each trait. Slide 21 of 31 End Show Copyright Pearson Prentice Hall

11– 3 Traits controlled by two or more genes are called a. multiple-allele traits. b. polygenic traits. c. codominant traits. d. hybrid traits. Slide 22 of 31 End Show Copyright Pearson Prentice Hall

11– 3 In four o'clock flowers, the alleles for red flowers and white flowers show incomplete dominance. Heterozygous four o'clock plants have a. pink flowers. b. white flowers. c. half white flowers and half red flowers. d. red flowers. Slide 23 of 31 End Show Copyright Pearson Prentice Hall

11– 3 A white male horse and a tan female horse produce an offspring that has large areas of white coat and large areas of tan coat. This is an example of a. incomplete dominance. b. multiple alleles. c. codominance. d. a polygenic trait. Slide 24 of 31 End Show Copyright Pearson Prentice Hall

11– 3 Mendel's principles apply to a. pea plants only. b. fruit flies only. c. all organisms. d. only plants and animals. Slide 25 of 31 End Show Copyright Pearson Prentice Hall

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