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Background Info Gregor Mendel – Austrian Monk (1822-1884) – Father of Genetics – Genetics – study of heredity – Heredity – passing of characteristics from parent to offspring. Background Info Gregor Mendel – Identified that all traits are controlled by a “factor” – This “factor” is a gene – GENE – section of a chromosome/DNA that codes for a trait. – TRAIT– characteristic passed from parent to offspring Genome • ALL of an organism’s genetic material Background Info Gregor Mendel • Studied Pea Plants to show how traits are passed from one generation to the next • He applied math to his observations • Studied pea plants because they came in 2 distinct forms Why did he choose the Pea Plant? • 1. The Structure of the Pea Flower • 2. The seven distinct traits (2 distinct forms) • 3. Rapid reproduction (Most pea plants reproduce in 90 days) Pea Plant Traits (Each trait only has 2 distinct forms) Genes & Alleles • Genes – chemical factors that determine traits (Flower color) • Alleles – different forms of genes that code for traits (Purple flowers or White flowers) Mendel found Dominant and Recessive Traits • An Allele is a distinct form of a gene • A dominant allele is the form that is visibly seen. • A recessive allele is the form that is there but not seen (unless there are 2 recessive alleles together). Symbols • Dominant Alleles – Capital Letters • Recessive Alleles – Lower Case Letters Genotypes • Genotype – Genetic makeup represented by symbols – AA, Aa, aa, TT, Bb, dd Phenotypes • Phenotype – Physical appearance expressed in words – Brown hair, Green eyes, Freckles Heterozygous • Heterozygous (different) – Gene pairs that carry one dominant and one recessive allele – Aa, Bb, Cc, Dd Homozygous • Homozygous (same) – Gene pairs that carry 2 dominant OR 2 recessive alleles – AA, aa, BB, bb Probability • Determining the likelihood of an event to occur • Can be shown in 3 ways – Fraction 1/2 – Percent 50% – Ratio 1:2 Hybrids & Purebreds • Hybrids receive different alleles from each parent (Hh, Bb, Zz) • Purebreds receive the same alleles from each parent (HH, bb, ZZ) Laws of Genetics • Law of Dominance: Dominant traits will always show over recessive traits • Law of Segregation: Alleles separate during meiosis • Law of Independent Assortment: gene pairs separate randomly and independently of each other Mendel’s Crosses • He started with 2 groups of purebred plants, called the P1 generation. 1. He crossed the purebreds by hand. 2. The P1’s offspring was called the F1 generation. The F1s then self-fertilized. 3. The F1’s offspring was known as the F2 generation. Monohybrid Crosses A genetic cross that looks at 1 trait • Cross a homozygous tongue roller with a nontongue roller • Genotype of parents – TT x tt t • Phenotypes of parents – Tongue roller, non-tongue roller • Possible Outcomes – Genotypic ratio • 100%Tt – Phenotypic ratio • 4 Tongue rollers:0 non-tongue rollers t T T Tt Tt Tt Tt Monohybrid Crosses • Cross 2 Heterozygous tongue rollers • Genotype of parents – Tt x Tt T T • Phenotypes of parents t TT Tt Tt tt – Tongue roller, Tongue roller • Possible Outcomes – Genotypic ratio • 1TT:2Tt:1tt – Phenotypic ratio • 3 tongue rollers: 1 nontongue roller t Monohybrid Crosses • Cross a heterozygous Tongue roller with a Non-Tongue roller • Genotype of parents T t – Tt x tt t Tt tt Tt tt • Phenotypes of parents – Tongue roller, non-tongue roller • Possible Outcomes – Genotypic ratio • 2Tt:2tt – Phenotypic ratio • 2 tongue rollers:2 nontongue rollers t Dihybrid Crosses • A genetic cross that looks at 2 traits • Cross 2 heterozygous green, round peas GgRr x GgRr G= green R= Round • Genotypic Ratio – 1:2:1:2:4:2:1:2:1 • Phenotypic Ratio – 9:3:3:1 g = yellow r = wrinkled Dihybrid Crosses GR Gr gR gr GR GGRR GG Rr Gg RR Gg Rr Gr GG Rr GG rr Gg Rr Gg rr gR Gg RR Gg Rr gg RR gg Rr gr Gg Rr Gg rr gg Rr gg rr