Mendelian Genetics 1 Gregor Johann Mendel Austrian monk

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 P 1 Generation = the parental generation; cross of purebred parents. Ex: round RR or wrinkled rr Offspring of P generation PRODUCES F 1 generation = the first-generation offspring. (1 st filial generation) 18

F 1 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 F 1 offspring produced: Genotype: 0 RR: 4 Rr: 0 rr Phenotype: Phenotype 4 Round: 0 wrinkled F 1 19

Generations F 2 generation = the second generation offspring. (2 nd filial generation) From breeding individuals from the F 1 generation 20

F 2 Monohybrid Cross Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Round seeds x Round seeds Rr x Rr F 1 offspring R r R RR Rr rr F 2 offspring produced: Genotype: 1 RR, 2 Rr, 1 rr Phenotype: Phenotype 3 Round & 1 wrinkled F 2 21

Another look at P, F 1, F 2 Cross 2 Results in Cross 2 Hybrids Pure all get Plants Hybrids 3 Tall & 1 Short TT x tt Tt 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