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Transcript
Genetics Gregor Mendel The father of Genetics • Genetics- the study of heredity • Heredity- the passing of characteristics or traits from parents to offspring • Mendel chose pea plants to research. Pea plants have male and female plants, so each have sex cells or gametes. male = pollen female = egg (in the pistil) Pollination- transfer of pollen to the pistil Fertilization- the uniting of male and female gametes Mendel’s Peas • When Mendel crossed 2 plants that were different in a single trait, he called that a monohybrid cross. • The resulting offspring were called the F1 generation or the first generation. (F stands for filial which means son/daughter) • The F1 generation plants were bred to give the F2 generation or the second generation. (the grandkids of the original plants) Alleles Mendel realized that genes controlled traits. – Alleles- different forms of the same gene – Each organism has 2 alleles for each trait (1 from mom and one from dad) on separate chromosomes Genotype & Phenotype Some alleles are dominant over others; they are the ones that show themselves Dominant = observed trait code (capital letters) Recessive = hidden trait code (lowercase letters) • The two allele codes (1 from each parent) make up the organisms genotype. (Bb) • Homozygous- the organism has 2 alleles that are the same for a trait; two capital letters or two lowercase letters Ex: TT or tt • Heterozygous- the organism has 2 alleles that are different; 1 capital letter and 1 lowercase letter Ex: Tt Genotype & Phenotype • The phenotype of the organism is its behavior and physical looks. (brown hair) Law of Segregation Law of Segregation- alleles from the organism separate to produce 2 types of gametes. Ex: An organism with a Bb genotype can produce a gamete carrying the B allele or a gamete carrying the b allele. Law of Independent Assortment Law of Independent Assortmentgenes for different traits are inherited independently of each other. Ex: just because you have brown hair you don’t have to be short Punnett Squares Punnett Squares- used to predict possible genotypes and phenotypes of the offspring. Monohybrid cross- one trait is crossed Ex: Tt x TT Dihybrid cross- 2 traits are crossed Ex: RrYy x RrYy Punnett Squares • Probability of a particular genotype or phenotype is determined with punnett squares. Punnett Squares Punnett Squares Cross a pea plant heterozygous yellow seeds with a green homozygous recessive pea plant. Yellow seeds are dominant to green. Punnett Squares Cross a pea plant homozygous dominant for purple flowers with a pea plant that is homozygous recessive for white flowers.