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What are some of the things you already know about heredity and genetics? (STAR book) Slide 2 What are some things you want to learn? Slide 3 Chapter 5.1 Have you ever wondered why some family members look very similar while others look very different? Slide 4 What were the results of Mendels experiments, or crosses? What controls the inheritance of traits in organisms? Section 1: Mendels Work Slide 5 Heredity Is the passing of physical characteristics from parent to offspring. Slide 6 Trait Each different form of a characteristic is called a trait. Slide 7 Fertilization The process of a new organism beginning to form due to the joining of a sperm and an egg cell. Slide 8 Purebred The offspring of many generations that have the same trait. Slide 9 Hybrid Is an organism that has two different alleles for a different trait. Slide 10 Hybrid Is an organism that has two different alleles for a different trait. Slide 11 Genes vs Alleles Genes are the factors that control a trait Alleles are the different forms of a gene Slide 12 Dominant vs Recessive Alleles Dominant always shows up Recessive is hidden by a dominant allele The only was a recessive allele shows up is if the organism has TWO recessive alleles for a particular trait. Slide 13 Black is dominant and white is recessive in bunnies Slide 14 Symbols for Alleles Geneticists use Letters Capital letters are used for dominant alleles Lower case are used for recessive alleles Slide 15 Crossing Pea Plants Gregor Mendel crossed pea plants that had different traits. The illustrations show how he did this. Slide 16 Mendels Experiments In all of Mendels crosses, only one form of the trait appeared in the F 1 generation. However, in the F 2 generation, the lost form of the trait always reappeared in about one fourth of the plants. Slide 17 Dominant and Recessive Alleles Mendel studied several traits in pea plants. Slide 18 Mendel's final Conclusions Each of the selected garden pea traits is controlled by a pair of alleles (uh-lee-uls) Slide 19 Mendel's final Conclusions Each of the selected garden pea traits is controlled by a pair of alleles (uh-lee-uls) For each trait, the offspring receives one allele from each parent Slide 20 Mendel's final Conclusions Each of the selected garden pea traits is controlled by a pair of alleles (uh-lee-uls) For each trait, the offspring receives one allele from each parent The chance of each offspring receiving one or the other allele is equal (50/50 chance) Slide 21 Mendel's final Conclusions Each of the selected garden pea traits is controlled by a pair of alleles (uh-lee-uls) For each trait, the offspring receives one allele from each parent The chance of each offspring receiving one or the other allele is equal (50/50 chance) The expression of a dominant trait only requires one dominant allele, recessive requires two recessive alleles. Slide 22 End of Section: Mendels Work HW: Please complete the Questions on page 159 (1abc- 2abc) in your STAR book