Presentation on theme: "Fundamentals Of Genetics"— Presentation transcript:
1 Fundamentals Of Genetics Chapter 9FundamentalsOfGeneticsRevised by: R. LeBlancBiology1/’12
2 Section 1 Mendel’s Legacy Chapter 9 ObjectivesDescribe 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.
3 Mendel's Legacy What is genetics? Section 1Mendel's LegacyWhat is genetics?The field of biology devoted to understanding how characteristics are transmitted from parents to offspring
4 Introduction to Mendel's Legacy Section 1Introduction to Mendel's LegacyHow 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, etcNote: Skin color and eye color are genetically controlled characteristics of alligators. Skin traits: white & brown; eye color traits: blue & brown
5 Mendel's Legacy List 5 characteristics that are passed on in families: Section 1Mendel's LegacyList 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
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)
12 Mendel’s ExperimentsMendel 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.
14 Mendel’s Results and Conclusions Recessive and Dominant TraitsMendel 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.
16 Mendel’s Results and Conclusions The Law of SegregationThe law of segregation states that a pair of factors is segregated, or separated, during the formation of gametes.The Law of Independent AssortmentThe 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.
17 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.
18 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.
19 Calculating Probability Section 2 Genetic CrossesChapter 9Calculating Probability
20 Punnett Square Method for Solving Genetics Problems Section 2 Genetic CrossesChapter 9Punnett Square Method for Solving Genetics Problems
21 A Cross Between One Pair of Contrasting Traits A Monohybrid crossA Cross Between One Pair of Contrasting TraitsPunnett 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:TTThe letters T and t represent alleles (characteristics of various traits)tTtTttTtTt
22 Monohybrid CrossGenotype 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 shortWhat 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 (Homozygous Dominant to Heterozygous to Homozygous recessive) Ex. 2 - Monohybrid CrossShow a cross between two heterozygous tall plants. Complete the Punnett square below and give the phenotypic and genotypic ratios for the possible offspring!TtPhenotype ratio3:1 (Tall to short)TTTTtGenotype ratio1:2:1(Homozygous Dominant toHeterozygous to Homozygous recessive)tttTt
24 Predicting Results of Monohybrid Crosses Chapter 9Section 2 Genetic CrossesPredicting Results of Monohybrid CrossesA 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.
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.FirstOutsideInsideLast
27 RY Ry rY ry (see blackboard) Dihybrid CrossesDihybrid 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.
28 Dihybrid Example #1 Each parent produces 4 possible gametes RY,rY,Ry,ryRyryRYrYRYRrYyRRYYRrYYRRYyRrYyrrYyrYRrYYrrYYRRYyRrYyRRyyRryyRyryrrYyRrYyRryyrryyPhenotypic Ratio = 9:3:3:1 (Round and Yellow, Round and Green, Wrinkled and yellow, Wrinkled and Green)
29 Note: G = green g = yellow and N = Smooth n = constricted Dihybrid Example #2What 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 andN = 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 gngN gn gN gnStep 3 (Fill in the Punnett Squares)Step 4 (Calculate Phenotype Ratio (what are the physical traits)gngnGnGngNGgNnGgNnggNnggNngnGgnnGgnnggnnggnngNGgNnGgNnggNnggNngnGgnnGgnnggnnggnn
31 Multiple Choice Chapter 9 Standardized Test PrepMultiple Choice1. 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 crossB. a dihybrid crossC. a hybrid crossD. a testcross
32 Multiple Choice, continued Chapter 9Standardized Test PrepMultiple Choice, continued1. 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 crossB. a dihybrid crossC. a hybrid crossD. a testcross
33 Multiple Choice, continued Chapter 9Standardized Test PrepMultiple Choice, continued2. In a monohybrid cross of two heterozygous parents (Pp), what would the expected genotypes of the offspring be?F. 1 PP : 2 Pp : 1 ppG. 1 pp : 3 PPH. 3 Pp : 1 ppJ. all Pp
34 Multiple Choice, continued Chapter 9Standardized Test PrepMultiple Choice, continued2. In a monohybrid cross of two heterozygous parents (Pp), what would the expected genotypes of the offspring be?F. 1 PP : 2 Pp : 1 ppG. 1 pp : 3 PPH. 3 Pp : 1 ppJ. all Pp
35 Multiple Choice, continued Chapter 9Standardized Test PrepMultiple Choice, continued3. Which of the following is an example of a genotype of a heterozygous individual?A. pB. YYC. ZzD. rr
36 Multiple Choice, continued Chapter 9Standardized Test PrepMultiple Choice, continued3. Which of the following is an example of a genotype of a heterozygous individual?A. pB. YYC. ZzD. rr
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