Mendelian Genetics Ch 14. Mendel Investigated variation in pea plants Studied traits in plants...
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Transcript of Mendelian Genetics Ch 14. Mendel Investigated variation in pea plants Studied traits in plants...
Mendelian GeneticsCh 14MendelInvestigated variation in pea plantsStudied traits in plantsParticulate theory of inheritanceGenes maintain integrity from generation to generation. Instead of blending together they act as discrete entities or particles.
Mendels lawsLaw of segregation- The two members of each gene pair segregate or separate into different gamete cells during the formation of eggs and sperm
Law of independent assortmentThe alleles of different genes are transmitted independently of each otherMendels single factor crossSingle factor cross, focused on one trait i.e. flower colorP purebred parents, WW x wwF1 all offspring were hybrid WwMonohybrid cross: Ww x WwF2 3:1 ratio
Looked at 2 factors,i.e. seed shape & colorP purebred parentsF1 all hybrids (for both factors)Dihybrid cross:RrYy x Rr YyResult: 9:3:3:1
Mendels two factor cross1 factor cross (monohybrid) practiceAxial flowers are dominant to terminal flowersWhat are the genotypic & phenotypic ratios of a cross between a plant with heterozygous axial flowers and a plant with terminal flowers?1. Choose letters to represent alleles2. Write genotypes of parents3. Write possible gametes for each parent4. Set up and complete punnett square5. Write genotypic ratio: DD: Dd: dd6. Write phenotypic ratio: Dominant: recessiveTest crossTo determine unknown parent with dominant phenotypeCross with a recessive homozygote
Tall dominant to short in pea plantsA cross between tall plant and short plant produces tall plants, short plants. What is the genotype of the tall plant?2 Factor cross (Dihybrid) - practiceIn rabbits Gray hair (G) is dominant to white (g), and Black eyes (B) are dominant to red (b).
Cross a heterozygous gray, red eyed rabbit with a homozygous gray, heterozygous black eyed rabbit; what is the phenotypic ratio?Determine gametes (use FOIL)Set up punnett squareDetermine phenotypic ratio: D/D: D/R: R/D: R/R (D = dominant, R = recessive)
CodominanceBoth alleles are expressedCRCR x CWCW Red flower, white flowerOffspring: CRCW red & white flower
Incomplete dominanceCRCR x CWCW Red flower, white flowerOffspring: CRCW hybrid is pink inbetween two parents
Multiple alleles: IA, IB, iShows Codominance, as well as complete dominance Multiple alleles more than 2 alleles for a character
Epistasis phenotypic expression of one gene is affected by another
Pleitropy ability of a gene to affect an organism in many ways, i.e. sickle cell disease has multiple effects
Effects of Sickle Cell allele Polygenic inheritance multiple genes affect a single phenotypic character
Polygenic inheritance of skin colorProbability & GeneticsRule of multiplication probability that two or more independent events occur togetherMultiply individual probabilities
Rule of addition probability of an event that can occur in two or more different ways Add separate probabilitiesSolving genetics problems by probability:
Hybrid Tall plants TtWhat is the probability of each parent having the recessive allele?1/2What is the probability of the parents producing a short plant? x =
Dihybrid crossYyRr x YyRrCan take each trait separatelyProbability of yellow offspring: YY, Yy = 3/4 green offspring: yy = 1/4Probability of round offspring: RR, Rr = 3/4 wrinkled offspring: rr = 1/4Probability Yellow & round x = 9/16yellow & wrinkled x = 3/16green & round x = 3/16green & wrinkled x = 1/16
Probability of yellow seed9/16 + 3/16 = 12/16 = 3/4