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Mendelian Genetics 1 Gregor Johann Mendel Austrian monk Studied inheritance in pea plants Called the “Father of Genetics" 2 Site of Gregor Mendel’s experimental garden in the Czech Republic 3 Mendel’s Pea Plant Experiments 4 Why peas, Pisum sativum? Can be grown in a small area Produce lots of offspring Produce pure plants when allowed to self-pollinate Can be artificially crosspollinated •Contain easily distinguishable traits 5 Seven Pea Plant Traits 6 Seven Pea Plant Traits 7 How Mendel Began Mendel produced pure strains by allowing the plants to selfpollinate for several generations 8 Mendel’s Experimental Methods Mendel hand-pollinated flowers using a paintbrush He could snip the stamens to prevent self-pollination He traced traits through the several generations 9 Genetics Terminology Trait - any characteristic that can be passed from parent to offspring. Ex: Eye Color 10 Genetics Terminology Heredity - passing of traits from parent to offspring Genetics - study of heredity 11 More Genetics Vocab Alleles - two forms of a gene (dominant & recessive) 12 More Genetics Vocab Dominant – allele that is expressed when present; represented by a capital letter (R) Recessive – allele that is only expressed when there are two present; represented by a lowercase letter (r) 13 More Terminology Genotype - gene combination for a trait (ex: BB, Bb, bb) Phenotype - the physical feature resulting from a genotype (ex: blue, brown) 14 Genotypes Homozygous- 2 dominant or 2 recessive genes (ex: TT or tt); also called purebred Heterozygous- one dominant & one recessive allele (ex: Tt); also called hybrid 15 Monohybrid Crosses •Monohybrid cross - cross involving a single trait. ex. flower color 16 Punnett Square Tool used to help solve genetics problems 17 Generations Parental P1 Generation = the parental generation; cross of purebred parents. Ex: round RR or wrinkled rr Offspring of P generation PRODUCES F1 generation = the first-generation offspring. (1st filial generation) 18 F1 Monohybrid Cross Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Round seeds x Wrinkled seeds Pure bred RR x rr parents r r R Rr Rr R Rr Rr F1 offspring produced: Genotype: 0RR: 4Rr: 0rr Phenotype: 4 Round: 0 wrinkled F1 19 Generations F2 generation = the second generation offspring. (2nd filial generation) From breeding individuals from the F1 generation 20 F2 Monohybrid Cross Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Round seeds x Round seeds Rr x Rr F1 offspring R r R RR Rr r Rr rr F2 offspring produced: Genotype: 1RR, 2Rr, 1rr Phenotype: 3 Round & 1 wrinkled F2 21 Another look at P, F1, F2 Cross 2 Pure Plants TT x tt Results in all Hybrids Tt Cross 2 Hybrids get 3 Tall & 1 Short TT, Tt, tt 22 Practice Punnett Squares **Please note: To earn full credit, you must include a key and cross with each problem!** 23 Construct a Punnett square to determine the probability of white flowers if a heterozygous purple (Pp) flower is crossed with a homozygous white (pp) flower. Key: __________________________ Cross: _________________________ Probability of white flowers = _____________ 24 Construct a Punnett square to determine the probability of short pea plants if a homozygous tall (TT) plant is crossed with a heterozygous tall (Tt) plant. Key: __________________________ Cross: _________________________ Probability of short plants= ________ Probability of tall plants= _________ 25 If round peas are dominant over wrinkled peas, make a Punnett square to determine the genotype and phenotype ratios of the offspring if a heterozygous plant is crossed with a homozygous recessive plant. Key: __________________________ Cross: _________________________ Genotype ratio: _________________ Phenotype ratio: _________________ 26