2 I. Introduction to Genetics 1. Gregor Mendel - “Father of Genetics”Austrian monk, teacher, scientist, gardenerFormulated basic laws of heredity in the early 1860s
3 2. Worked with garden peas because: Easy to grow and had a short generation timeCould be self-pollinated3. Chose varieties that were true-breedingNo genetic variation for a trait4. Studied 7 simple traits
5 6. Principle of Dominance and Recessiveness F1 plants resembled only one of the parentsF1 hybrids contained two different factors (alleles) for each traitone dominant; (masks recessive);one recessive; (seems to disappear)
7 7. Principle of Segregation Organism contains two factors for each trait.Alleles separate from one another during formation of gametes.Each gamete contains one allele for each trait.
8 8. Principle of Independent Assortment Each trait is independent of anotherGenes of one pair of traits assort independentlyAll combinations of genes occur in gametes
9 II. Chromosomes, Genes, & Genetic Crosses Homologous Chromosomes contain genes (locations on DNA for traits) for the same traitsTraits are controlled by alleles (alternative forms of a gene).3. Genotype refers to the alleles an individual receives at fertilization4. Phenotype refers to the physical appearanceof the individual.
10 5. Homozygous dominant genotypes = two dominant alleles for a trait. (BB)6. Homozygous recessive genotypes =possess two recessive alleles for a trait (bb)7. Heterozygous genotypes =one of each allele for a particular trait (Bb)Review:True-breeding organisms would be homozygous dominant OR recessive individuals.Hybrids would be heterozygous
11 Show probabilities of future offspring. 8. Punnett SquaresShow probabilities of future offspring.A monohybrid cross = cross betweenindividuals that involve 1 contrasting trait.
12 9. Monohybrid Crosses Examples Ex. 1: One is heterozygous for round seeds x one with wrinkled seedsRrPhenotype/Genotype ChartRrrrrPhenotypeGenotype(s)RoundWrinkledRR & RrrrRrrrPlant #1’s genotype:Plant #2’s genotype:RrrrGenotype probability:______________Genotype ratio:___________________Phenotype probability:_____________Phenotype ratio:__________________
13 B. Example 2 & 3: P & F1 cross for true-breed tall x true breed short PhenotypeGenotype(s)P cross F1 crossTallTT, TtShortttTtTtT tTTttT TtTt25% pure tall50% hybrid tall25% pure short100% Tall100% Heterozygous(Homozygous x Homozygous) (Heterozygous x Heterozygous)
15 Complete and diagram the 3 types of monohybrid crosses below. Round peas are dominant to wrinkled peas. Cross a homozygous dominant x homozygous recessive.Short plants are recessive to tall plants. Cross a homozygous recessive x heterozygousGreen peas are dominant to yellow peas cross a heterozygous x heterozygous
16 Round peas are dominant to wrinkled peas Round peas are dominant to wrinkled peas. Cross a homozygous dominant x homozygous recessive.PhenotypeGenotype(s)
17 2. Short plants are recessive to tall plants 2. Short plants are recessive to tall plants. Cross a homozygous recessive x heterozygousPhenotypeGenotype(s)
18 3. Green peas are dominant to yellow peas cross a heterozygous x heterozygous PhenotypeGenotype(s)
19 10. Test CrossesA cross of an individual of unknown genotype with an individual of known genotype.(has to be homozygous recessive)Results tells if unknown individual is heterozygous or homozygousVery important to breeders
25 Both Brown and white expressed at the same time. ROAN
26 White & Red Mixed – RW (“roan”) Ex: Red Coat - RRWhite Coat – WWWhite & Red Mixed – RW (“roan”)R RR WRWRWRWRWRRWRWRWRWWWAll Roan – both red and white hair1 red : 2 roan : 1 white
27 3. Multiple Allele Traits are traits with 3 or more alleles; only get 2 1. ABO Blood group system; types – A, B, AB, O2. IAIA =type A IAi = type A ii = type OIBIB= type B IBi = type B IAIB= type AB*A,B codominant *Both dominant to O
29 IA IB IB IAIB IBIB IBIB IB IAIB What are the possible blood types when aPerson with AB blood and a person that is homozygous for B blood reproduce?PhenotypeGenotype(s)Type AIAIA , IAiType BIBIB , IBiType ABIAIBType OiiIAIBIBIAIBIBIBType AB & B are possibleIBIBIBIAIB
30 IA IA IB IAIB IAIB IAIB IB IAIB What are the possible blood types when aPerson with homozygous A blood and a person that is homozygous for B blood reproduce?PhenotypeGenotype(s)Type AIAIA , IAiType BIBIB , IBiType ABIAIBType OiiIAIAIBIAIBIAIBType AB onlyIAIBIBIAIB
31 IB i IBi ii i i IBi ii What are the possible blood types when a Person with B blood and a person with O blood reproduce?PhenotypeGenotype(s)Type AIAIA , IAiType BIBIB , IBiType ABIAIBType OiiIBiIBiiiiiIBiii
33 RrYy RrYy X RrYy Ry RY rY ry Law of Independent Assortment: Genes for different traits are inherited independentlyR, r, Y, y go to sperm/egg independently of each otherCan recombine in four ways:RyRYRrYyrYry
34 3. Dihybrid Cross: A cross involving two pairs of contrasting traits A = feathersC = crestPhenotypesBlue feathersRed feathersw/ Crestw/o CrestGenotypesaaAA, AaCC, CcccPhenotypesRed feathers, w/ CrestRed feathers, w/o CrestBlue feathers, w/ CrestBlue feathers, w/o CrestGenotypesAACC, AACc, AaCC, AaCcAAcc, AaccaaCC, aaCcaacc
35 Example Cross P1: RRYY x rryy yellow, round green, wrinkled (homozygous) (homozygous)RYRYRYRYOffspring are all heterozygousryRrYyRrYyRrYyRrYyRrYyRrYyryRrYyRrYyRrYyryRrYyRrYyRrYyryRrYyRrYyRrYyRrYy
36 round, yellow: round, green : wrinkled, yellow: wrinkled ,green: 9Round seeds are dominant to wrinkled and yellow is dominant to green. What are all the possible phenotypes?3round, yellow: round, green : wrinkled, yellow: wrinkled ,green:3RrYy X RrYy1Phenotypic Ratio is 9:3:3:1RYRyrYryRYryrYRyRRYYRRYyRrYYRrYyRRyyRryyrrYYrrYyrryy
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