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11-1 Gregor Mendel 11-2 Punnett Squares

Learn about Gregor Mendel, the father of genetics, and his experiments with pea plants. Explore the concepts of dominant and recessive alleles, inheritance, and the use of Punnett squares to predict genetic outcomes.

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11-1 Gregor Mendel 11-2 Punnett Squares

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  1. 11-1 Gregor Mendel 11-2 Punnett Squares

  2. Bell Work • What are dominant and recessive alleles? Alleles are forms of a gene. The dominant form of an allele is the form whose trait shows up if it is present. The recessive allele is the form whose trait only shows up when the dominant allele is not present.

  3. Bell Work Why do children resemble their parents? They inherit their parents characteristics through alleles- forms of genes.

  4. 11-1 Inheritance Every living thing has a set of characteristics inherited from its parent or parents. Heredity holds the key to understanding what makes each species unique.

  5. 11-1 1. The scientific study of heredity is called _____. Genetics

  6. 11-1 Gregor Mendel Who was Gregor Mendel? An Austrian monk, born in 1822. His experiments with pea plants laid the foundations of the science of genetics.

  7. 11-1 Gregor Mendel’s Peas 2. What do we know as true about Gregor Mendel’s garden peas? • The male portion of the plant produces sperm (in pollen). The female portion of the plant produces egg cells. • Fertilization produces a new cell, which develops into a tiny embryo encased within a seed. • Pea Plants are normally self-pollinating.

  8. 11-1 3. What does it mean when pea plants are described as being true breeding? It means that if they are allowed to self-pollinate, they would produce identical offspring.

  9. 11-1 4. To perform his experiments, how did Mendel prevent pea flowers from self-pollinating and control their cross-pollination? To prevent self-pollination, Mendel cut the pollen bearing male part and dusted this pollen onto another flower. This process is known as cross-pollination.

  10. 11-1 5. Genes – C chemical factors that determine traits 6. Hybrids B the offspring of crosses between parents with different traits

  11. 11-1 7. Traits A specific characteristics that vary from one individual to another 8. Alleles D different forms of a gene

  12. 11-1 9. The principle of dominance states… that some alleles are dominant and some alleles are recessive. 10. True or False: An organism with a recessive allele for a particular form of a trait will always exhibit that form. False- The organism with a recessive allele will only exhibit that form when the dominant allele for the trait is not present.

  13. 11-1 11.Which traits were controlled by dominant alleles in Mendel’s pea plants? Tall & Yellow Which traits were controlled by recessive alleles? Short & Green

  14. 11-1 Mendel called each original pair of plants the P Generation (parental) and the offspring of these the F1 generation (first filial) Mendel produced hybrids when he crossed parents with different traits; and to his surprise the offspring only resembled one of the parents.

  15. 11-1 Segregation Mendel wanted to know the answer to another question: Had the recessive alleles disappeared, or were they still present in the F1 plants? P generation F1 Generation F2 Generation

  16. 11-1 12. How did Mendel find out whether the recessive alleles were still present in the F1 plants? He allowed all seven kinds of F1 hybrid plants to produce an F2 generation.

  17. 11-1 13. About one fourth of the F2 plants from Mendel’s F1 crosses showed the trait controlled by the ______ allele. Recessive

  18. 11-1 Results of the F1 Cross 14. A** Mendel assumed that a dominant allele had masked the corresponding recessive allele in the F1 generation. • However, the trait controlled by the recessive allele showed up in some of the F2 plants. • D ** This reappearance indicated that at some point, the allele for shortness was segregated, or separated, from the allele for tallness. • Mendel suggested that the alleles for tallness and shortness in the F1 plants segregated from one another during the formation of the gametes. 15. What are gametes? • Gametes are the Sex Cells

  19. F1 Generation T t T t Gametes T t T t F2 Generation T T T t T t t t 11-1 17.

  20. 11-3 17. In the diagram, the dominant allele is represented by ___ and the recessive allele is represented by ___. T dominant t recessive

  21. 11-2 Probability and Punnett Squares 1. The likelihood that a particular event will occur is called ___________. Probability 2. What is the probability that a single coin flip will come up heads? 50%

  22. 11-2 3. True or False: The past outcomes of coin flips greatly affect the outcomes of future coin flips. False: past outcomes do not affect future ones 4. Why can the principles of probability be used to predict the outcomes of genetic crosses? The way in which alleles segregate is completely random, like a coin flip.

  23. 11-2 5. How do geneticists use Punnett Squares? The gene combinations that might result from a genetic cross can be determined by drawing a diagram known as a Punnett Square. 6. How do we complete the Punnett Square for Tt x Tt T t T t

  24. Tt x TtPunnett Square

  25. Monohybrid Cross Complete the Punnett Square:

  26. Punnett Square Solution

  27. 11-2 Matching 7. Genotype- D. Genetic makeup of an organism (Tt) 8. Homozygous – A Organisms that have two identical alleles for a particular trait (TT or tt)

  28. 11-2 Matching 9. Phenotype- C Physical characteristic of an organism 10. Heterozygous- B Organisms that have two different alleles for the same trait (Tt)

  29. 11-2 11. True or False: Homozygous organisms are true-breeding for a particular trait. True: TT true-breeding Tt hybrid 12. True or False: Plants with the same phenotype always have the same genotype. False

  30. Yellow vs Green Plants If Y is Dominant Yellow and y is recessive green Which of the following plants would be yellow? • YY • Yy • yy

  31. 11-2 13. Which are true about probability and segregation? B, C, and D • Is True If : In an F1 cross between two hybrid tall pea plants (Tt), ¼of the F2 plants will have two alleles for tallness (TT)

  32. 11-2 14. In Mendel’s model of segregation, what was the ratio of tall plants to short plants in the F2 generation? 3:1 3 Tall plants for every 1 short plant

  33. 11-2 15. True or False: Probabilities predict the precise outcome of an individual event. False: probabilities predict the average outcome 16. How can you be sure of getting the expected 50:50 ratio of flipping a coin? Flip the coin many times

  34. 11-2 17. The __________ the number of offspring from a genetic cross, the closer the resulting numbers will get to expected values. larger 18. True or False: The ratios of an F2 generation are more likely to match Mendelian predicted ratios if the F1 generation contains hundreds or thousands of individuals. True

  35. Check for Understanding What is the difference between genotype and phenotype? Genotype: the set of genes in our DNA which is responsible for a particular trait. Phenotype: the physical expression, or characteristics, of that trait.

  36. 11-3 • In a two-factor cross, Mendel followed _____ different genes as they passed from one generation to the next. Two

  37. 11-3 2. Phenotype Genotype round yellow peas RRYY wrinkled green peas rryy

  38. 11-3 3. The F1 offspring of Mendel’s two factor cross was c. heterozygous dominant with round yellow peas RrYy

  39. 11-3 4. T/ F The genotypes of the F1 offspring indicated to Mendel that genes assort independently. False

  40. 11-3 5. How did Mendel produce the F2 offspring? self-pollination in F1

  41. 11-3 6. Which phenotypes would Mendel expect to see if genes segregated independently? c. round and green d. wrinkled and yellow

  42. 11-3 7. What did Mendel observe in the F2 offspring that showed him that the alleles for seed shape segregate independenlty of those for seed color? F2 had combination of phenotypes not present in the P generation round green & wrinkled yellow

  43. 11-3 8. What were the phenotypes of the F2 generation that Mendel observed? round green RRyy round yellow RRYY wrinkled green rryy wrinkled yellow rrYY

  44. 11-3 9. What was the ratio of Mendel’s F2 generation for the two-factor cross? 9:3:3:1 10. Complete the Punnett Square to show the predicted results of Mendel’s two-factor cross

  45. F2 Generation

  46. 11-3 11. State Mendel’s principle of independent assortment: R genes & Y genes separate independently during meiosis/ gamete formation.

  47. 11-3 12. The following is true about Mendel’s principles: a. The inheritance of biological characteristics is determined by genes that are passed from parents to their offspring. c. The copies of genes are segregated from each other when gametes are formed d. The alleles for different genes usually segregate independently of one another.

  48. 11-3 13. When two or more forms of the gene for a single trait exist, some forms of the gene may be ____ and others may be ____ dominant recessive

  49. 11-3 14. T/ F All genes show simple patterns of dominant and recessive alleles. False

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