Mendel punett squares2traitcrosses


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Mendel punett squares2traitcrosses

  1. 1. Mendel & His Plants! Gregor Mendel bred pea plants and recorded inheritance patterns in the offspring.
  2. 2. Mendel’s Experiment Mendel bred true-breeding plants When self-fertilized, a true-breeding plant produces offspring identical in appearance to itself generation after generation.
  3. 3. Mendel’s Experiment Mendel crossed 2 plants- 1 true-breeding for purple and 1 true- breeding for white (P generation) Hegot the following results: (F1 generation)
  4. 4. How did he cross the plants?
  5. 5. Step 2: Crossing the F1 generation Onetrait is dominant Onetrait is recessive Ratio of Dominant : recessive 12 purple: 4 white = 3 purple: 1 white
  6. 6. Interest Grabber continued Section 11-1 Mendel’s Results Parents (P) First Generation (F1) Second Generation (F2) Long stems × short stems All long 787 long: 277 short Red flowers × white flowers All red 705 red: 224 white Green pods × yellow pods All green 428 green: 152 yellow Round seeds × wrinkled seeds All round 5474 round: 1850 wrinkled Yellow seeds × green seeds All yellow 6022 yellow: 2001 greenGo toSection:
  7. 7.  1. In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics? 2. How do the characteristics of the second generation compare to the characteristics of the first generation?
  8. 8. Using Diagrams to show inheritance: Punnett Squares Alleles= P P p p alternativ e forms of genesP = Pp P p purple p= white P p P p
  9. 9. A B C D F12345
  10. 10. Rules for Punnett Squares 1. Draw a square Place the traits for each parent across the top and side (alleles) Bring down the alleles from the top and across from the side Write the final ratio for the genotype & phenotype Add proper vocab terms (homozygous/heterozygous AND Dom & Recessive)
  11. 11. Perform the following cross from the F1 generation using a Punnett Square
  12. 12. Try Another!
  13. 13. Inheritance & Probability We have been examining inheritance using probablilty Probabilities predict AVERAGES! Not individuals. The offspring may not exactly match the predicted outcome (the larger the sample, the closer the expected values)
  14. 14.  25% WW (homozygous dominant) 25% ww (homozygous recessive) 50% Ww (heterozygous) 75% White 25% Black Will it always turn out this way???
  15. 15. Two Factor/ Two Trait Crosses Law of Segregation  Alleles separate from one another during meiosis Law of Independent Assortment  Alleles segregate independently of one another (one does not depend on the other)
  16. 16. Two Trait Crosses Separatethe alleles using the FOIL method (kind of like a )R rYy RY Ry rY ryRrYy x RrYy
  17. 17. RY Ry rY ry RY Ry rY ry RrYy xRrYy
  18. 18. Two Trait CrossesGenotypic Ratio:1/16 RRYY 1/8 Rryy1/8 RRYy 1/8 rrYy1/16 RRyy 1/16 rrYY1/8 RrYY 1/16 rryy¼ RrYy
  19. 19. Phenotypic Ratio9 Yellow Round 3 Yellow wrinkled 3 green round 1 green wrinkled ALLHeterozygote two-trait crosses will result in a 9:3:3:1 ratio
  20. 20. Phenotypic Ratio for 2 trait crosses9 dominant dominant 3 dominant recessive 3 recessive dominant 1 recessive recessive
  21. 21. A Few Different Types of Inheritance
  22. 22. A New Kind of Inheritance Heterozygous phenotype is a blending of the recessive and dominant traits. What kind of inheritance? Incomplete Dom.
  23. 23. Codominance The dominant AND the recessive are both expressed RR x rr
  24. 24. Multiple Alleles Genes with more than two alleles. Ex: Rabbits C = full color; dominant to all other alleles  Cch = chinchilla, partial defect in pigmentation, dominant to ch and c alleles  ch Himilayan, color on certain parts of the body  c= albino, no color
  25. 25. cchch? Cc?cc? chc?
  26. 26. Codominant Cross Predictthe genotypic and phenotypic ratio of a cross between a Full Color Rabbit (Cch) and a himilayan (chc). Genotype:25% Cch, 25%Cc, 25% chch, chc Phenotype: 50% Full color, 50% himilayan
  27. 27. Sex-Linked Genes Even the X and Y chromosomes code for traits Since males only have one X chromosome, all traits are expressed… even the recessive! This explains why males are much more likely to develop  Colorblindness  Hemophilia  Duchenne Muscular Dystrophy These are all genes on the X chromosome!
  28. 28. Sex Linked Cross XH YXH X X H H XH YXh XH Xh XhY
  29. 29. X-Inactivation How many X chromosomes do females have? How many X chromosomes do males have? Why do females need 2?