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

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

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

Introduction to Mendel's Legacy 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

Mendel's Legacy List 5 characteristics that are passed on in families: 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.

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

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

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.

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)

Plant Reproductive Organs

Mendel’s Experiment

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 the F1 generation. Offspring of the F1 generation were called the F2 generation.

Three Steps of Mendel’s Experiments

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 the dominant trait. The trait that was masked was called the recessive trait.

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

Mendel’s Results and Conclusions The Law of Segregation The law of segregation states that a pair of factors is segregated, or separated, during the formation of gametes. The Law of Independent Assortment The law of independent assortment states 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.

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

Objectives Chapter 9 Section 2 Genetic Crosses Differentiate between the genotype and the phenotype of an organism. Explain how probability is used to predict the results of genetic crosses. Use a 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. Differentiate a monohybrid cross from a dihybrid cross.

Calculating Probability Section 2 Genetic Crosses Chapter 9 Calculating Probability

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

A Cross Between One Pair of Contrasting Traits 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

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)

(Homozygous Dominant to Heterozygous to Homozygous recessive) 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

Predicting Results of Monohybrid Crosses 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.

Section 2 Genetic Crosses Chapter 9 Testcross

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

RY Ry rY ry (see blackboard) 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 square show the possible offspring that may be produced from these parents.

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 ry rrYy RrYy Rryy rryy Phenotypic Ratio = 9:3:3:1 (Round and Yellow, Round and Green, Wrinkled and yellow, Wrinkled and Green)

Note: G = green g = yellow and N = Smooth n = constricted 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

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

Multiple Choice 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

Multiple Choice, continued 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

Multiple Choice, continued 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

Multiple Choice, continued 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

Multiple Choice, continued 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

Multiple Choice, continued 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