Module 6 - Mendelian Genetics PDF

MODULE 6 Mendelian Genetics BIO 001– Modern Biology ENGR. AL R. ROMANO Faculty, Department of Environmental and Sanitary Engineering College of Engineering and Architecture...

MODULE 6 Mendelian Genetics BIO 001– Modern Biology ENGR. AL R. ROMANO Faculty, Department of Environmental and Sanitary Engineering College of Engineering and Architecture Technological institute of the Philippines-Quezon City  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Outline 1. Basic Genetic Terminology 2. Mendelian Genetics 3. Monohybrid Crosses 4. Using Probability to predict Genetic Crosses 5. Dihybrid Crosses- genetic crosses two genes involved 6. Goodness-of fit/ Chi-Squared test  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Genetics and its importance Genetics is the field of biology devoted to understanding how characteristics Genetic diversity in dogs is are transmitted from parents to a broad and complex topic offspring. given the wide variety of Genes influence our lives. dog breeds and their evolutionary history Genes contribute to personality Genes are fundamental to who and what we are Genes affect our susceptibility to many diseases and disorders Curved Bones Shortened Limbs Hand deformation  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Genetic Terminology Gene - A genetic factor (region of DNA) that helps determine a characteristic Allele - One of two or more alternative forms of a gene Locus - Specific place on a chromosome occupied by an allele Genotype - Set of alleles possessed by an individual organism Heterozygote - An individual organism possessing two different alleles at a locus Homozygote - An individual organism possessing two of the same alleles at a locus Phenotype or trait - The appearance or manifestation of a character Character or characteristic -An attribute or feature  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Genetic Terminology MODULE 6.1 Fundamentals of Genetics BIO 001– Modern Biology  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Gregor Mendel: Mendel’s Legacy Austrian Monk Father of Modern Genetics Mendel's knowledge of statistics later proved valuable in his research on heredity-the transmission of characteristics from parents to offspring. Although he studied many plants, he is remembered most for his experiments with Pisum sativum, a species of garden peas  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Mendel’s Garden Peas The pea characteristics that Mendel observed were:  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Mendel’s Garden Peas Pea Characteristics Description Traits Studied Seed Shape Round or Wrinkled Round (dominant) / Wrinkled (recessive) Seed Color Yellow or green Yellow (dominant) / Green (recessive) Flower Color Purple or White Purple (dominant) / White (recessive) Pod Shape Inflated or constricted Inflated (dominant) / Constricted (recessive) Pod Color Green or Yellow Green (dominant) / Yellow (recessive) Flower Position Axial or Terminal Axial (dominant) / Terminal (recessive) Plant Height Tall or Short Tall (dominant) / Short (recessive)  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Mendel’s Method Mendel was able to observe how traits were passed from one generation to the next by carefully controlling how pea plants were pollinated. Pollination occurs when pollen grains produced in the male reproductive parts of a flower, called the anthers, are transferred to the female reproductive part of a flower, called stigma. Self-pollination occurs when pollen is transferred from the anthers of a flower to the stigma of either that flower or another flower on the same plant. Mendel controlled the breeding Cross-pollination can be performed by manually of his pea plants and tracked transferring pollen from the flower of a second plant the inheritance of traits by to the stigma of the antherless plant. transferring pollen from the anthers of one plant to the stigma of another plant.  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Mendel’s Experiments He began by growing plants that were true-breeding for each trait. Plants that are true-breeding, or pure, for a trait always produce offspring with that trait when they self-pollinate. Mendel produced true-breeding plants by self-pollinating the pea plants for several generations, (as shown in the next slide). He eventually obtained 14 true-breeding plant types, one for each of the 14 traits observed. Mendel cross-pollinated pairs of plants that were true-breeding for contrasting traits of a single characteristic. He called the true- breeding parents the P generation. When the plants matured, Mendel recorded the number of each type of offspring produced by each cross. He called the offspring of the P generation the first filial generation, or 𝑭𝟏 generation. He then allowed the flowers from the F, generation to self-pollinate and collected the seeds. Mendel called the plants in this generation the second filial generation, or 𝑭𝟐 generation.  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Gregor Mendel Mendel bred plants for several generations that were true breeding for specific traits. These plants he called the P generation. He then observed the passage of these specific traits through successive generations  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Mendel’s Experiments P Generation P Generation Male: Purple flowers Female: white flowers F1 Generation F1 Generation 100% purple Some traits are Dominant Some traits are Recessive F2 Generation F2 Generation 75% purple; 25% White (3:1) Offspring won’t always resemble the parents Traits can skip generation  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Mendel’s Experiment  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Mendel’s Result and Conclusions 1. Recessive and dominant traits (LAW of Dominance) Mendel hypothesized that the trait appearing in the 𝐹1 generation was controlled by a dominant factor because it masked, or dominated, the factor for the other trait in the pair. He thought that the trait that did not appear in the 𝐹1 generation but reappeared in the F₂ generation was controlled by a recessive factor.  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Mendel’s Result and Conclusions 2. Law of Segregation Mendel concluded that the paired factors separate during the formation of reproductive cells. That is, each reproductive cell, or gamete, receives one factor of each pair. When two gametes combine during fertilization, the offspring have two factors for each characteristic. The law of segregation states that a pair of factors is segregated, or separated, during the formation of gametes  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Mendel’s Result and Conclusions 3. Law of Independent Assortment Mendel concluded that the factors for individual characteristics are not connected. The law of Independent assortment states that factors separate independently of one another during the formation of gametes.  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Support for Mendel’s Conclusions  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Support for Mendel’s Conclusions Because chromosomes occur in pairs, genes also occur in pairs. Each of two or more alternative forms of a gene is called an allele. Mendel's factors are now called alleles. Letters are used to represent alleles. Capital letters refer to dominant alleles, and lowercase letters refer to recessive alleles During meiosis, gametes receive one chromosome from each homologous pair of chromosomes. Thus, when the gametes combine in fertilization, the offspring receives from each parent one allele for a given trait. MODULE 6.2 Genetics Crosses BIO 001– Modern Biology  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Genotype and Phenotype Genotype- organism's genetic makeup; consists of the alleles that the organism inherits from its parents. Example: Combination of 1 dominant, 1 recessive allele. Types of Genotypes a. Homozygous Dominant: combination of 2 dominant alleles b. Homozygous Recessive: Combination of 2 recessive allele c. Heterozygous: Combination of 1 dominant, 1 recessive allele. Phenotype- organism's appearance; The phenotype of a PP or a Pp pea plant is purple flowers, whereas the phenotype of a pp pea plant is white flowers  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Genotype and Phenotype ASPECT GENOTYPE PHENOTYPE Definition The genetic makeup of an The observable characteristics organism of an organism Composition Specific alleles (e.g., "AA," "Aa," Physical traits (e.g., flower color, "aa") height) Influence Determines potential traits Result of genotype and environmental factors Expression Not directly visible; requires Directly visible and measurable testing  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Recall Allele: The different flavors of genes (B or g) (i.e Blood alleles, flower color alleles.) Dominant Allele: B Blue Eyes Recessice Allele: g Green Eyes Homozygous Dominant: BB Blue Eyes Homozygous Recessive: gg Green Eyes Heterozygous: Bg Blue Eyes  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Recitation 1. Which choice(s) are genotypes? 2. Which choice(s) are heterozygous genotypes? 3. Which choice(s) are phenotypes?  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Probability Probability is the likelihood that a specific event will occur. Expressed as a decimal, a percentage, or a fraction. Probability is determined by the following equation: probabilities are represented on a scale from one to zero. The closer to 0, the worse the chances; the closer to 1, the better  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Laws of Probability Law of Mutually Exclusive Events (Addition Rule) Mutually exclusive events cannot occur at the same time. If one event occurs, the other cannot. Example: Coin flip or Dice when events are mutually exclusive, the sum of the probabilities of all the possible events will always equal one How is it related to Genetics?  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Laws of Probability Law of Independent Events (Product Rule) Independent events are events whose outcomes do not affect each other. The occurrence of one event does not change the probability of the other event. Example: Lottery In lottery, each number is an independent event (no impact with another). The product rule states that the probability of getting the number (let say 4 in dice) is the product of their individual probability (1/6 * 1/6). How is it related to Genetics?  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Example In Mendel's experiments, the dominant trait of yellow seed color appeared in the F₂ generation 6,022 times. The recessive trait of green seed color appeared 2,001 times. Determine the probability that the dominant trait will appear in a similar cross.  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Example If the probability of being blood-type A is 1/8 and the probability of blood-type O is 1/2, what is the probability of being either blood-type A or O? a. 5/8 Does the problem fall under the addition or multiplication rule? b. ½ c. 1/8 Using Addition Rule of Probability: d. 1/16 1 1 𝟓 + = 8 2 𝟖  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Predicting Results of Monohybrid Crosses A cross in which only one characteristic is tracked is a monohybrid cross. The offspring of a monohybrid cross are called monohybrids. Example: A cross between a pea plant that is true-breeding for producing purple flowers and one that is true-breeding for producing white flowers is an example of a monohybrid cross. Biologists use a diagram called a Punnett square, to aid them in predicting the probable distribution of inherited traits in the offspring. Monohybrid cross for flower’s color  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Punnett Squares Genetics tools used to predict offspring probability. A pea plant homozygous for purple flowers that is crossed with a pea plant homozygous for white flowers will produce only purple-flowering offspring. Note that all of the offspring, called monohybrids are heterozygous for flower color. Steps in Constructing Punnett Square: 1. Set up the Punnett Square/Grid. Label the genotypes of the parents 2. Fill in the Square by combining the top and side alleles in each box 3. Analyze the results  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Punnett Squares P generation Punnett Square p p Defined: Genetics tools used to predict offspring PP pp P Pp Pp probability Setting up Punnett F1 generation squares: P Pp Pp 1. Parent genotypes on outside of the squares 100% = Purple 2. Simply fill in each square 3. Inside squares F2 generation represent the possible offspring genotypes  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Punnett Squares P generation Punnett Square Defined: Genetics tools used to predict offspring probability PP pp P p Setting up Punnett F1 generation squares: P PP Pp 1. Parent genotypes on outside of the squares 2. Simply fill in each square Pp Pp Pp Pp p Pp pp 3. Inside squares F2 generation represent the possible offspring genotypes 75% = Purple 25% = White  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Punnett Squares Examples A cross between a Guinee pig that is homozygous dominant for the trait of black coat color(BB) and a Guinee pig that is heterozygous for this trait (Bb). Two possible genotypes can result from this cross: 1. Bb : 50 % The probable phenotype is black coat color in every case 2. BB: 50 % In rabbits, the allele for black coat color (B) is dominant over the allele for brown coat color (b). The Punnett square shows the predicted results of crossing Homozygous x Heterozygous two rabbits that are heterozygous (Bb) for coat color. Three possible genotypes can result from this cross: 1. BB : 25 % The probable phenotype is 2. Bb : 50 % 75% of the offspring are 3. bb: 25 % predicted to have black coat. Heterozygous x Heterozygous  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Recitation Cross a heterozygous yellow (Yy) seeded pea plant with a homozygous recessive green (yy) seeded pea plant 1. List the offspring genotypes Y y 2Yy, 2yy 2. List the offspring phenotypes y Yy yy 2 yellow, 2 green 3. What is the probability of growing a homozygous dominant pea plant y Yy yy 0% 4. What is the probability of growing yellow seeds? 50%  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Genotypic Ratio vs. Phenotypic Ratio The ratio of the genotypes that appear in offspring is called genotypic ratio. Example: the genotypic ratio of the monohybrid cross represented in the figure is 1 BB : 2 Bb : 1 bb. The ratio of the offspring phenotypes is called phenotypic ratio. Example: the phenotypic ratio of the monohybrid cross represented in the figure is 3 black: 1 brown.  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Complete and Incomplete Dominance Complete Dominance- If one allele was completely dominant over another. (For example: both pea plants PP and Pp for flower color have purple colors) Incomplete Dominance- If offspring have a phenotype in between that of the parents. Example: Snapdragons with 3 phenotype flower color  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Codominance occurs when both alleles for a gene are expressed in a heterozygous offspring. In codominance, neither allele is dominant or recessive, nor do the alleles blend in the phenotype. Allele symbols may vary:  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Dihybrid Crosses Dihybrid crosses are a type of genetic cross Steps in constructing dihybrid cross: that examines the inheritance of two 1. Write the parent cross using 16 square- different traits, each controlled by Punnett square. separate genes (Law of independent assortment). 2. Write the gamete combinations from the parents (use foil method) when solving genetics problems using dihybrid crosses (or tri or tetra) always break the problem down into the individual monohybrid problem (and then you can use simple Punnett squares)  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Dihybrid Crosses example If a heterozygous round, yellow seeded plant mates with another heterozygous round, yellow seeded plant, what proportion of the offspring will have round, yellow seeds? Rr Yy RRYY RRYy RrYY RrYy Rr Yy RRYy RRyy RrYy Rryy Using Foil Method: RrYY RrYy rrYY rrYy RY Ry rY ry RrYy Rryy rrYy rryy  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Dihybrid Crosses Genotype Ratios (Probability): RRYY 1/16 = 6.25% RRYy 2/16 = 12.5% RrYY 2/16 = 12.5% RrYy 4/16 = 25% Rryy 2/16 = 6.25% what proportion of the offspring will have round, yellow seeds? rrYy 2/16 = 12.5% RRYY RRYy RrYY RrYy rryy 1/16 = 6.25% Using Addition Rule: rrYY 2/16 = 12.5% 1 2 2 4 𝟗 + + + = = 𝟓𝟔. 𝟐𝟓% RRyy 1/16 = 6.25% 16 16 16 16 𝟏𝟔  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Chi-Square Test the Goodness-of-Fit test takes real world experimental data (which NEVER perfect) and tests it. It is used to see if observed values for a set of data are similar to or significantly different from expected values. Phenotype Observed (O) Round Seeds 5,474 Wrinkled Seeds 1,850 Are these observed values similar or not to the expected values?  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Chi-Square Test (𝑂 − 𝐸 ) 2 2 𝑖 𝑖 𝑥 =෍ 𝐸𝑖 Where: 𝑂𝑖 = Observed value 𝐸𝑖 = Expected value  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Chi-Square Test Example Consider the following:  Technological Institute of the Philippines-QC 938 Aurora Blvd., Cubao, Quezon City Environmental and Sanitary Engineering Department BIO 001|Modern Biology Chi-Square Test Example Consider the following information: Determine if there is a significant difference in the expected and observed values.  THANK YOU Questions? References of photos are still to be indicated.