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Mendelian Genetics Learning Goal: How are traits passed down from parents to offspring?

Mendelian Genetics Learning Goal: How are traits passed down from parents to offspring?. Concept 1 : Analyzing the effects of classic Mendelian genetic crosses such as monohybrid, dihybrid , testcross , and applying to pedigree diagrams . PART 2. Try This!.

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Mendelian Genetics Learning Goal: How are traits passed down from parents to offspring?

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  1. Mendelian GeneticsLearning Goal: How are traits passed down from parents to offspring? Concept 1: Analyzing the effects of classic Mendelian genetic crosses such as monohybrid, dihybrid, testcross, and applying to pedigree diagrams. PART 2

  2. Try This! • An organism with the genotype AaBb is crossed with an organism that has the genotype AABb. • What are all the possible gametes of each individual parent? • What is the probability that any of the offspring has the AABB genotype? • If A and B exhibit complete dominance, what is the probability of the offspring exhibiting both the A and B phenotypes?

  3. Try This! • An organism with the genotype AaBb is crossed with an organism that has the genotype AABb. • What are all the possible gametes of each individual parent? AaBb x AABb AB ABAbAb aBab • What is the probability that any of the offspring has the AABB genotype? AABB – 2 punnet squares! AA: ½ BB: ¼ ½ x ¼ = 1/8 • If A and B exhibit complete dominance, what is the probability of the offspring exhibiting both the A and B phenotypes? What genotypes give dominance for A and B? A_B_ A_: 1 B_: ¾ 1 x ¾ = 3/4

  4. Concept 1: Analyzing the effects of classic Mendelian genetic crosses such as monohybrid, dihybrid, testcross, and applying to pedigree diagrams. • Terms associated with genetics problems: P, F1, F2, dominant, recessive, homozygous, heterozygous, phenotypic, and genotypic • How to derive the proper gametes, genotypes, and phenotypes, when working a genetics problem (monohybrid, dihybrid, testcross) • The difference between an allele and a gene • How to read a pedigree (monohybrid, dihybrid, testcross)

  5. Make Math Work for YOU! • Rule of Multiplication: • Independent events happening at the same time • “this and that together” • Example: three coins are flipped. The probability that all three coins show tails is • ½x ½ x ½ = 1/8

  6. Make Math Work for YOU! • Rule of Addition • Mutually exclusive events • “this or that” “different ways of getting the same thing” • Example: three coins are flipped. What is the probability of getting one tail and two heads? • - tail, head, head 1/8 (½ x ½ x ½ rule of multiplication) • - head, head, tail 1/8 • - head, tail, head 1/8 • The probability that two coins are heads and one is tail is: 1/8+ 1/8 + 1/8 = 3/8

  7. Tips for working through genetics problems: • THERE IS NO MAGICAL FORMULA!!!! • What do you HAVE? • What do you WANT? • Plan a way to get there using a combination of: • punnet squares • probabilities • logic

  8. Try This! • In peas, yellow seed colour is dominant over green seed colour, and round seed shape is dominant over wrinkled seed shape. • A round-yellow seeded plant was crossed with a green-wrinkled seeded plant producing 20 plants: 11 of these plants has yellow-round seeds, and 9 of these plants had green-round seeds. • What was the probable genotypes of the parent plants?

  9. Tips for working through genetics problems: • Write down the allele symbols using the same letter for a gene: • upper case for dominant (ex: Yellow – Y) • lower case for recessive (ex: green – y). • Write down the phenotypes for each individual.

  10. Tips for working through genetics problems: • Write down possible genotypes for each individual. • If the phenotype is recessive, genotype must be homozygous recessive (green = yy) • If the phenotype is dominant, genotype is either homozygous dominant or heterozygous. (yellow = YY or Yy, can write Y_) • If the phenotype is “true-breeding,” the genotype is homozygous for that trait.

  11. Tips for working through genetics problems: • Write down what you are looking for in the question. • If you need to find genotype/phenotypes of offspring (or “grandchildren”), complete the cross (Yy x yy) and use the probability rules or the Punnet square. • If you need to find genotypes/phenotypes of parents or (or “grandparents”), deduce by working backwards and reasoning. (Note: numbers of offspring may be actual rather than predicted by ratios… 1:1 ratio may be 13 individuals:15 individuals)

  12. Shortcuts! • 3:1 ratio indicates a monohybrid cross (Aa x Aa) • 1:1 ratio indicates a cross of a heterozygote with a homozygous recessive (Aa x aa) • All offspring identical to parents suggests a cross of parents that are homozygous for the same trait, or homozygous dominant with heterozygous (AA x AA or aa x aa or AA x Aa) • 9:3:3:1 ratio indicates a dihybrid cross (AaBb x AaBb) • 1:1:1:1 ratio indicates a cross of a dihybrid with a double homozygous recessive (AaBb x aabb)

  13. We just need to practice… • Try… On Worksheets:Multiple Choice: 1, 2, 3, 5, 7, 8, 10, 13Genetics Problems: 1, 2, 6, 12, 13 Learning Goal: How are traits passed down from parents to offspring?

  14. Pedigrees…

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