Studying Heredity Chapter 8 Section 8-3. Objectives for section 8-3 Predict results of genetic crosses w/Punnett Square Predict results of genetic crosses

Download Studying Heredity Chapter 8 Section 8-3. Objectives for section 8-3 Predict results of genetic crosses w/Punnett Square Predict results of genetic crosses

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  • Studying HeredityChapter 8 Section 8-3

  • Objectives for section 8-3Predict results of genetic crosses w/Punnett SquareDescribe how a testcross can be used to determine genotypeDefine & analyze a simple pedigreePG. 170

  • Punnett Squarepredicts possible outcomes of genetic crosses Inventor Reginald Punnett

  • Monohybrid Cross

    1. Assign letters for traits2. Determine parents genotypes4. Fill in each box of the Punnett square 3. Write genotypes across top & side 5. State genotype and phenotype

  • A heterozygous dimpled female marries a heterozygous male. What are the possible outcomes of their children?D

  • Test cross: dominant phenotype/unknown genotype (x) w/ homozygous recessiveBreeders need to know if organism- heterozygous/ homozygous dominant for a characterWhy?

  • EX: A plant w/ yellow seeds & unknown genotype (Y?) is test crossed with a plant that has green seeds (yy).

  • V. Dihybrid Crosses =2 contrasting traitsCross 2 pea plants heterozygous for seed shape AND seed color1. R=round r=wrinkled AND Y=yellow y=green2. Parents genotypesa. RrYy x RrYy3. Possible Gametes??a. RY, Ry, rY, ry

  • Typical Dihybrid Cross

    4. Phenotypic ratio9 round, yellow3 round, green3 wrinkled, yellow1 wrinkled greenTypical dihybrid cross ratio: 9:3:3:1

  • Monohybrid vs. Dihybrid CrossMonohybrid: involves one trait with a phenotypic ratio for the F2 generation of 3:1

    Dihybrid: involves two traits with a phenotypic ratio for the F2 generation of 9:3:3:1

  • Why use Punnett Squares?A. Improve cropsB. Improve domestic animalsC. Determine risk for genetic disordersD. Predict expected results of genotypes or phenotypes

  • Probability likelihood that a specific event will occurA. Expressed in words, decimals, fractions, or percentagesB. Probability= # of 1 kind of possible outcome/total # of all possible outcomesC. Both parents must be considered when calculating probability D. To find probability, multiply the separate probabilities of the two events

  • Pedigree: family history-shows a trait inherited over several generationsHelps in tracking genetic disordersColorblindness Pedigree

  • What is determined from a pedigree?Autosomal: gene will appear in both sexes equally Sex-linked: allele located only on the X chromosome & are recessive a. Males carrying recessive allele on X chromosome exhibit sex-linked characterWhy??b. Females-less chance of exhibiting sex-linked conditionWhy??

  • Pedigree for the Albino Trait Pedigree for HemophiliaSex linked!! Only affectedautosomal

  • 3. Autosomal Dominant: every individual w/condition has a parent w/condition 4. Recessive: individual w/ condition can have 1, 2, or neither parent exhibit the condition

  • 5. Homozygous dominant or heterozygous: phenotype will show the dominant allele6. Homozygous recessive: phenotype shows the recessive allele

    Can 2 people who are heterozygouscarriers of a recessive mutation have children with the mutation??

  • Hemophilia-the Royal disease1 in 10,000 1 in 100,000,000

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