Chapter 9

1. Chapter 9 Fundamentals Of Genetics Revised by: R. LeBlanc Biology 1/’12

2. Section 1 Mendel’s Legacy Chapter 9 Objectives • Describehow Mendel was able to control how his pea plants were pollinated. • Describethe steps in Mendel’s experiments on true-breeding garden peas. • Distinguishbetween dominant and recessive traits. • Statetwo laws of heredity that were developed from Mendel’s work. • Describehow Mendel’s results can be explained by scientific knowledge of genes and chromosomes.

3. Section 1 Mendel's Legacy • What is genetics? • The field of biology devoted to understanding how characteristics are transmitted from parents to offspring

4. Section 1 Introduction to Mendel's Legacy • How does this alligator differ from other alligators? (Notes: This is NOT an albino and NOT a different species, but it just has different traits (genetic condition) which are rare.) • White and brown are contrasting traits of skin color. • What are other characteristics that are examples of contrasting traits? • Did you write down: color, height, texture, etc Note: Skin color and eye color are genetically controlled characteristics of alligators. Skin traits: white & brown; eye color traits: blue & brown

5. Section 1 Mendel's Legacy • List 5 characteristics that are passed on in families: • Did you list: eye color, hair color, etc ?? • Name one characteristic that may also be inherited but that is also influenced by behavior or environment: • Muscle size, body weight, having a suntan, height.

6. Mendel’s Experiment • Observe the pea plants in the given image. • List the noticeable characteristics of the pea plants: • See the next slide

7. Mendel’s 7 Characteristics: • Seed shape • Seed color • Flower color • Flower position • Pod color • Pod shape • Plant height

8. Mendel's Legacy • “Father of Genetics” – 1800’s • Carried out the first experiments on heredity using pea plants. • Carefully controlled his experiments, studying only one trait at a time and analyzed data mathematically. • Was the first to succeed in predicting how traits are transferred from generation to generation. • Heredity-Passing on of characteristics from parent to offspring. • Genetics- Branch of biology that studies inherited traits.

9. Plant reproductive terms • GAMETES - Male or Female sex cell. In plants, pollen (male) and ovule (female). • FERTILIZATION- Fusion of the male and female gametes within the flower. • POLLINATION - Transfer of pollen from the anther to the pistil, usually by wind, water, or insects. • CROSS-POLLINATION - Transfer of pollen from one flower (tall) to another flower (short)

10. Plant Reproductive Organs

11. Mendel’s Experiment

12. Mendel’s Experiments • Mendel bred plants for several generations that were true-breeding for specific traits and called these the P generation. • Offspring of the P generation were called theF1 generation. • Offspring of the F1 generation were called theF2 generation.

13. Three Steps of Mendel’s Experiments

14. Mendel’s Results and Conclusions • Recessive and Dominant Traits • Mendel concluded that inherited characteristics are controlled by factors that occur in pairs. • In his experiments on pea plants, one factor in a pair masked the other. The trait that masked the other was called thedominant trait. The trait that was masked was called therecessivetrait.

15. Section 1 Mendel’s Legacy Chapter 9 Mendel’s Conclusions

16. Mendel’s Results and Conclusions • The Law of Segregation • Thelaw of segregationstates that a pair of factors is segregated, or separated, during the formation of gametes. • The Law of Independent Assortment • Thelaw of independent assortmentstates that factors for individual characteristics are distributed to gametes independent of one another. • The law of independent assortment is observed only for genes that are located on separate chromosomes or are far apart on the same chromosome.

17. Support for Mendel’s Conclusions • We now know that the factors that Mendel studied arealleles, or alternative forms of a gene. • One allele for each trait is passed from each parent to the offspring.

18. Chapter 9 Section 2 Genetic Crosses Objectives • Differentiatebetween the genotype and the phenotype of an organism. • Explainhow probability is used to predict the results of genetic crosses. • Usea Punnett square to predict the results of monohybrid and dihybrid genetic crosses. • Explain how a testcross is used to show the genotype of an individual whose phenotype expresses the dominant trait. • Differentiatea monohybrid cross from a dihybrid cross.

19. Section 2 Genetic Crosses Chapter 9 Calculating Probability

20. Section 2 Genetic Crosses Chapter 9 Punnett Square Method for Solving Genetics Problems

21. A Monohybrid cross A Cross Between One Pair of Contrasting Traits • Punnett Square - Prediction of offspring (F1) using genotypes from parents (P) • Using the letters T= tall and t= short show a cross between a homozygous dominant and homozygous recessive plant. • Example #1: T T The letters T and t represent alleles (characteristics of various traits) t Tt Tt t Tt Tt

22. Monohybrid Cross • Genotype Ratio:This ratio list the number of off-spring with the 3 possible allele combinations: • Homozygous Dominate : Heterozygous : Homozygous Recessive • (PURE DOMINANT : MiXeD DoMiNaNt : pure recessive) • Phenotype Ratio:This ratio list the number of off-spring with physical trait characteristics: • Example: # of Tall : # of short • What would be the Genotype and Phenotype ratios for Example #1? • Genotype Ratio 0 : 4 : 0 (Pure tall / mixed tall / short) • Phenotype Ratio 4 : 0 (Tall / short)

23. Ex. 2 - Monohybrid Cross • Show a cross between two heterozygous tall plants. Complete the Punnett square below and give the phenotypic and genotypic ratios for the possible offspring! T t Phenotype ratio 3:1 (Tall to short) T TT Tt Genotype ratio 1:2:1 (Homozygous Dominant to Heterozygous to Homozygous recessive) t tt Tt

24. Chapter 9 Section 2 Genetic Crosses Predicting Results of Monohybrid Crosses • A testcross, in which an individual of unknown genotype is crossed with a homozygous recessive individual, can be used to determine the genotype of an individual whose phenotype expresses the dominant trait.

25. Section 2 Genetic Crosses Chapter 9 Testcross

26. Law of Independent Assortment • Traits are inherited independently of each other. • To determine which trait a parent will contribute during fertilization, the F.O.I.L Method is used. First Outside Inside Last

27. Dihybrid Crosses • Dihybrid cross - Cross between two pairs of contrasting traits. Ex. Cross a pea plant with heterozygous round and heterozygous yellow pea plant with a pea plant that has the same genotype. (Round is dominant over wrinkled; and Yellow is dominant over green) • First,identify the correct genotype for each parent. • (RrYy x RrYy). • Next,identify all the possible types of gametes each parent can produce. (use the F.O.I.L. Method) • RY Ry rY ry (see blackboard) • Using a punnett squareshow the possible offspring that may be produced from these parents.

28. Dihybrid Example #1 Each parent produces 4 possible gametes RY,rY,Ry,ry ry Ry RY rY RY RrYy RRYY RrYY RRYy RrYy rrYy rY RrYY rrYY RRYy RrYy RRyy Rryy Ry rrYy ry RrYy Rryy rryy Phenotypic Ratio = 9:3:3:1 (Round and Yellow, Round and Green, Wrinkled and yellow, Wrinkled and Green)

29. Dihybrid Example #2 • What are the genotype and phenotype ratios in the offspring resulting from a cross between two pea plants; a heterozygous Green, constricted plant with a yellow , heterozygous Smooth plant. Note: G = green g = yellow and N = Smooth n = constricted

30. Dihybrid Example #2 • Step 1 (Parents Genotype?) • Ggnn x ggNn • Step 2 (F.O.I.L for each parents gametes) • Gn Gn gn gn • gN gn gN gn • Step 3 (Fill in the Punnett Squares) • Step 4 (Calculate Phenotype Ratio (what are the physical traits) gn gn Gn Gn gN GgNn GgNn ggNn ggNn gn Ggnn Ggnn ggnn ggnn gN GgNn GgNn ggNn ggNn gn Ggnn Ggnn ggnn ggnn

31. Chapter 9 Standardized Test Prep Multiple Choice 1. What is a procedure in which an individual of unknown genotype is crossed with a homozygous recessive individual to determine the genotype of the unknown individual called? A. a monohybrid cross B. a dihybrid cross C. a hybrid cross D. a testcross

32. Chapter 9 Standardized Test Prep Multiple Choice, continued 1. What is a procedure in which an individual of unknown genotype is crossed with a homozygous recessive individual to determine the genotype of the unknown individual called? A. a monohybrid cross B. a dihybrid cross C. a hybrid cross D. a testcross

33. Chapter 9 Standardized Test Prep Multiple Choice, continued 2. In a monohybrid cross of two heterozygous parents (Pp), what would the expected genotypes of the offspring be? F. 1 PP : 2 Pp : 1 pp G. 1 pp : 3 PP H. 3 Pp : 1 pp J. all Pp

34. Chapter 9 Standardized Test Prep Multiple Choice, continued 2. In a monohybrid cross of two heterozygous parents (Pp), what would the expected genotypes of the offspring be? F. 1 PP : 2 Pp : 1 pp G. 1 pp : 3 PP H. 3 Pp : 1 pp J. all Pp

35. Chapter 9 Standardized Test Prep Multiple Choice, continued 3. Which of the following is an example of a genotype of a heterozygous individual? A. p B. YY C. Zz D. rr

36. Chapter 9 Standardized Test Prep Multiple Choice, continued 3. Which of the following is an example of a genotype of a heterozygous individual? A. p B. YY C. Zz D. rr