Mendelelian Genetics Mendelian Genetics 1/16/2019 copyright cmassengale

Gregor Mendel (1822-1884) Discovered the laws of HEREDITY Mendelian Genetics 1/16/2019 Gregor Mendel (1822-1884) Discovered the laws of HEREDITY copyright cmassengale

Gregor Johann Mendel Austrian monk Mendelian Genetics 1/16/2019 Gregor Johann Mendel Austrian monk Studied the inheritance of traits in pea plants Mendel's work was not recognized until the turn of the 20th century copyright cmassengale

Mendelian Genetics 1/16/2019 Gregor Johann Mendel Between 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants He found that the plants' offspring retained traits of the parents Called the “Father of Genetics" copyright cmassengale

Traits Genetics – study of how traits are passed from parent to offspring

Particulate Inheritance Mendelian Genetics 1/16/2019 Particulate Inheritance Mendel stated that physical traits are inherited as “particles” Mendel did not know that the “particles” were actually Chromosomes & DNA copyright cmassengale

Traits are determined by the genes on the chromosomes Traits are determined by the genes on the chromosomes. A gene is a segment of DNA that determines a trait.

P (Parent generation) F1 F2 (3:1)

Why peas, Pisum sativum? Can be grown in a small area Mendelian Genetics 1/16/2019 Why peas, Pisum sativum? Can be grown in a small area Produce lots of offspring Produce pure plants when allowed to self-pollinate several generations Can be artificially cross-pollinated copyright cmassengale

Mendelian Genetics 1/16/2019 copyright cmassengale

Mendelian Genetics 1/16/2019 copyright cmassengale

Humans have 46 chromosomes or 23 pairs. One set from dad – 23 in sperm One set from mom – 23 in egg

Mendelian Genetics 1/16/2019 Genetics Terminology Dominant allele- stronger of two genes expressed in the hybrid; represented by a capital letter (R) Recessive allle - gene that is masked by the dominant allele; represented by a lowercase letter (r) copyright cmassengale

Genetics Terminology Phenotype – expressed traits (observable) Mendelian Genetics 1/16/2019 Genetics Terminology Genotype- genetic make-up (letters) Ex. AA, Aa, aa Phenotype – expressed traits (observable) Ex. Tall, short, brown hair copyright cmassengale

Genetics Terminology Heterozygous genotype – different alleles Ex. Aa Mendelian Genetics 1/16/2019 Genetics Terminology Homozygous genotype- same alleles Ex. AA, aa Heterozygous genotype – different alleles Ex. Aa copyright cmassengale

Genetics Terminology Alleles– alternate forms of a gene Ex. A and a Mendelian Genetics 1/16/2019 Genetics Terminology Gene- section of DNA or chromosome that codes for a PROTEIN or TRAIT Alleles– alternate forms of a gene Ex. A and a A and A copyright cmassengale

Mendelian Genetics 1/16/2019 Genetic Terminology Trait - any characteristic that can be passed from parent to offspring Heredity - passing of traits from parent to offspring Genetics - study of heredity copyright cmassengale

Types of Genetic Crosses Mendelian Genetics 1/16/2019 Types of Genetic Crosses Monohybrid cross - cross involving a single trait e.g. flower color Dihybrid cross - cross involving two traits e.g. flower color & plant height copyright cmassengale

Mendelian Genetics 1/16/2019 Monohybrid Crosses copyright cmassengale

P1 Monohybrid Cross r r Rr Rr R R Rr Rr Trait: Seed Shape Mendelian Genetics 1/16/2019 P1 Monohybrid Cross Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Round seeds x Wrinkled seeds RR x rr Genotype: Rr Phenotype: Round Genotypic Ratio: All alike Phenotypic Ratio: All alike r r Rr Rr R R Rr Rr copyright cmassengale

P1 Monohybrid Cross Review Mendelian Genetics 1/16/2019 P1 Monohybrid Cross Review Homozygous dominant x Homozygous recessive Offspring all Heterozygous (hybrids) Offspring called F1 generation Genotypic & Phenotypic ratio is ALL ALIKE copyright cmassengale

F1 Monohybrid Cross R r RR Rr R r Rr rr Trait: Seed Shape Mendelian Genetics 1/16/2019 F1 Monohybrid Cross Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Round seeds x Round seeds Rr x Rr Genotype: RR, Rr, rr Phenotype: Round & wrinkled G.Ratio: 1RR:2Rr:1rr P.Ratio: 3:1 R r RR Rr R r Rr rr copyright cmassengale

F1 Monohybrid Cross Review Mendelian Genetics 1/16/2019 F1 Monohybrid Cross Review Heterozygous x heterozygous Offspring: 25% Homozygous dominant RR 50% Heterozygous Rr 25% Homozygous Recessive rr Offspring called F2 generation Genotypic ratio is 1:2:1 Phenotypic Ratio is 3:1 copyright cmassengale

Breed the P1 generation tall (TT) x dwarf (tt) pea plants t T Mendelian Genetics 1/16/2019 Breed the P1 generation tall (TT) x dwarf (tt) pea plants t T copyright cmassengale

tall (TT) vs. dwarf (tt) pea plants Mendelian Genetics 1/16/2019 Solution: tall (TT) vs. dwarf (tt) pea plants T t All Tt = tall (heterozygous tall) produces the F1 generation Tt copyright cmassengale