Gregor Johann Mendel Austrian monk, mathematician by trade Mendelian Genetics 12/4/2018 Gregor Johann Mendel Austrian monk, mathematician by trade Studied the inheritance of traits in pea plants Developed the laws of inheritance Mendel's work was not recognized until the turn of the 20th century 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"

Mendelian Genetics 12/4/2018 Site of Mendel’s experimental garden in the Czech Republic Note the ratio of flower colors… Fig. 5.co

Mendelian Genetics 12/4/2018 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

Mendel’s Pea Plant Experiments Mendelian Genetics 12/4/2018 Mendel’s Pea Plant Experiments

Mendel’s Experimental Methods Mendelian Genetics 12/4/2018 Mendel’s Experimental Methods Mendel hand-pollinated flowers using a paintbrush He snipped the stamens to prevent self-pollination Covered each flower with a cloth bag He traced 8 traits through the several generations Ultimately he produced pure strains for each

Mendelian Genetics 12/4/2018

Mendelian Genetics 12/4/2018

Mendel’s Flowers Once the pure strains were made; Mendel then began systematically crossing plants, this time however, he let the plants self-pollinate. Why? He observed the offspring produced for each trait, in each generation, for any patterns that appeared. Mendel’s questions: If traits are known, can the inheritance of the traits in offspring be predicted? What is the ‘mechanism’ for inheritance?

Mendelian Genetics 12/4/2018 Generation “Gap” Parental P1 Generation = the parental generation in a breeding experiment, the pure strain F1 generation = the first-generation offspring in a breeding experiment. (1st filial generation) F2 generation = the second-generation offspring in a breeding experiment. (2nd filial generation)

White trait reappeared WHY no white? What happened to the white trait? White trait reappeared in this generation, so there must be some ‘factor’ in the purple flower that masked it

Mendelian Genetics 12/4/2018 Mendel’s Conclusions Dominant – trait that was expressed if present; represented by a capital letter (R) Recessive – trait that is expresses only if the dominant is not present; represented by a lowercase letter (r) Factors: sequence of DNA that codes for a trait, today we know those are the GENES Alleles - two forms of a gene (dominant & recessive) Ex: Trait(Gene)=Flower Color Alleles=Purple/White Regardless of the trait, results were the same and could be predicted in future generations…Mendel developed his first law of genetics; the Law of Dominance Maternal Chromosome Paternal Chromosome

Mendelian Genetics 12/4/2018 Law of Dominance In a cross of parents(P) that are pure for contrasting traits, only one form of the trait will appear in the next generation(F1). All the offspring will be heterozygous and express only the dominant trait. RR x rr yields all Rr

Mendelian Genetics 12/4/2018 Mendelian Genetics

Eight Pea Plant Traits GENE ALLELES GENE ALLELES Mendelian Genetics 12/4/2018 Eight Pea Plant Traits GENE ALLELES GENE ALLELES

Let’s see how it works, by adding the allele notations… RR rr Rr Rr x Rr Rr rr RR Rr

Predictable Generations Mendelian Genetics 12/4/2018 Predictable Generations Cross 2 Pure Plants TT x tt Results in all Hybrids Tt Cross 2 Hybrids get 3 Tall & 1 Short TT,Tt,Tt,tt

You try one…Let’s use Seed Color P generation YY yy Yy Yy Yy Yy F1 All Yy, yellow YY Yy Yy yy ¾ yellow ¼ YY, 2/4 Yy ¼ green ¼ yy F2 YY Yy Yy yy

GENOTYPEs Genotype - allele combination for a trait Mendelian Genetics 12/4/2018 GENOTYPEs Genotype - allele combination for a trait Homozygous – allele combination involving two of the same alleles; can be either Homozygous dominant: RR Homozygous recessive: rr Heterozygous – allele combination of one dominant & one recessive allele  Heterozygous: Rr

PHENOTYPE Phenotype - the physical features resulting from the genotype; am I… Phenotype also refers to your chemical features as well; enzymes and functional proteins are also determined by genes and allele combinations PURPLE or, am I WHITE

Genotype & Phenotype in Seed Color Mendelian Genetics 12/4/2018 Genotype & Phenotype in Seed Color Genotype of alleles: R = yellow seed r = green seed In the F2 The possible combinations are: SPIDERMAN Genotypes RR Rr rr Phenotypes YELLOW YELLOW GREEN

Mendelian Genetics 12/4/2018 Punnett Squares Diagram that is used to predict an outcome of a particular cross or breeding experiment Illustrate Mendel’s second law Law of Segregation

Mendelian Genetics 12/4/2018

Mendelian Genetics CROSSES INVOLVING 1 GENE: 2 ALLELES 12/4/2018 Monohybrid crosses CROSSES INVOLVING 1 GENE: 2 ALLELES

P1 Monohybrid Cross r r Rr Rr R R Rr Rr Trait: Seed Shape Mendelian Genetics 12/4/2018 P1 Monohybrid Cross Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Round seeds x Wrinkled seeds RR x rr r r Genotype: Rr Ratio: 1:1 or 100% Phenotype: Round Ratio: 1:1 or 100% Rr Rr R R Rr Rr

F1 Monohybrid Cross R r RR Rr R r Rr rr Trait: Seed Shape Mendelian Genetics 12/4/2018 F1 Monohybrid Cross Trait: Seed Shape Alleles: R – Round r – Wrinkled Cross: Round seeds x Round seeds Rr x Rr Genotype: RR, Rr, rr Ratio: 1:2:1 Phenotypes: Round & wrinkled Ratio: 3:1 R r RR Rr R r Rr rr

P1 Monohybrid Cross Review Mendelian Genetics 12/4/2018 P1 Monohybrid Cross Review Homozygous dominant x Homozygous recessive Offspring all Heterozygous (hybrids) Offspring called F1 generation Genotypic & Phenotypic ratio is ALL ALIKE

F1 Monohybrid Cross Review Mendelian Genetics 12/4/2018 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

Results of Monohybrid Crosses Mendelian Genetics 12/4/2018 Results of Monohybrid Crosses Inheritable factors or genes are responsible for all heritable characteristics Phenotype is based on Genotype Each trait is based on two genes, one from the mother and the other from the father True-breeding individuals are homozygous ( both alleles) are the same

Law of Independent Assortment Mendelian Genetics 12/4/2018 Law of Independent Assortment Alleles for different traits are distributed to sex cells (& offspring) independently of one another. This law can be illustrated using dihybrid crosses.

Mendelian Genetics 12/4/2018 Dihybrid Cross A breeding experiment that tracks the inheritance of two traits. Mendel’s “Law of Independent Assortment” a. Each pair of alleles segregates independently during gamete formation b. Formula: 2n (n = # of heterozygotes)

Answer: 1. RrYy: 2n = 22 = 4 gametes RY Ry rY ry Mendelian Genetics 12/4/2018 Answer: 1. RrYy: 2n = 22 = 4 gametes RY Ry rY ry 2. AaBbCCDd: 2n = 23 = 8 gametes ABCD ABCd AbCD AbCd aBCD aBCd abCD abCD 3. MmNnOoPPQQRrssTtQq: 2n = 26 = 64 gametes

All possible allele combinations Mendelian Genetics 12/4/2018 Dihybrid Cross Traits: Seed shape & Seed color Alleles: R round Y yellow r wrinkled y green To help determine allele combinations use the math order of operations FOIL First-Outside-Inside-Last RrYy x RrYy RY Ry rY ry RY Ry rY ry All possible allele combinations

Dihybrid Cross RY Ry rY ry RY Ry rY ry Rryy RRYy RrYY RrYy Mendelian Genetics 12/4/2018 Dihybrid Cross RY Ry rY ry RY Ry rY ry Rryy RRYy RrYY RrYy RRYy Rryy RrYy Rryy RrYY RrYy rrYY rrYy RrYy Rryy rrYy rryy

Dihybrid Cross Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 Mendelian Genetics 12/4/2018 Dihybrid Cross Round/Yellow: 9 RRYY 1 RRYy 2 RrYY 2 RrYy 4 Round/green: 3 RRyy 1 Rryy 2 wrinkled/Yellow: 3 rrYY 1 rrYy 2 wrinkled/green: 1 Rryy 1 9:3:3:1 phenotypic ratio RY Ry rY ry RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy rryy

Mendelian Genetics 12/4/2018 Dihybrid Cross Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1

Mendelian Genetics 12/4/2018 copyright cmassengale Question: How many gametes will be produced for the following allele arrangements? Remember: 2n (n = # of heterozygotes) 1. RrYy 2. AaBbCCDd 3. MmNnOoPPQQRrssTtQq

Genetic Practice Problems Mendelian Genetics 12/4/2018 copyright cmassengale Genetic Practice Problems

Breed the P1 generation tall (TT) x dwarf (tt) pea plants t T Mendelian Genetics 12/4/2018 copyright cmassengale Breed the P1 generation tall (TT) x dwarf (tt) pea plants t T

tall (TT) vs. dwarf (tt) pea plants Mendelian Genetics 12/4/2018 copyright cmassengale Solution: tall (TT) vs. dwarf (tt) pea plants T t All Tt = tall (heterozygous tall) produces the F1 generation Tt

Breed the F1 generation tall (Tt) vs. tall (Tt) pea plants T t T t Mendelian Genetics 12/4/2018 copyright cmassengale Breed the F1 generation tall (Tt) vs. tall (Tt) pea plants T t T t

tall (Tt) x tall (Tt) pea plants Mendelian Genetics 12/4/2018 copyright cmassengale Solution: tall (Tt) x tall (Tt) pea plants T t produces the F2 generation 1/4 (25%) = TT 1/2 (50%) = Tt 1/4 (25%) = tt 1:2:1 genotype 3:1 phenotype TT Tt tt