Gregor Mendel Understanding Heredity Objectives Describe how Mendel

Gregor Mendel Understanding Heredity

Objectives Describe how Mendel applied the principles of probability to inheritance. � Learn of Mendel’s famous pea experiment. � Understand that a Punnett square is a visual representation of the relative probabilities of offspring outcomes, for both genotypes and phenotypes. � Examine the law of dominance. �

HEREDITY The passing on of traits from parents to offspring

GENES The basic unit of inheritance by which characteristics are passed from one generation to the next.

Gregor Mendel The Father of Genetics The causes of heredity remained a mystery for centuries… Late 1850’s - Gregor Mendel breed green pea plants � Used the general rules of probability to explain the basic principles of heredity � Probability – › Predicts the likelihood of random events › Used to estimate the likelihood of gene distribution from one generation to the next. › A number between 0 and 1 represents the probability of an outcome. �An impossible event = 0 �Something that is certain to occur = 1 � VIDEO The Life of Gregor Mendel (23 minutes) VIDEO - Gregor Mendel and Pea Plants

Mendel’s Question Why are some traits found in the parents showing up in their offspring, while other traits are not?

ALLELES The different forms a gene may have for a trait › A variation of a gene ›

Gregor Mendel Pea Plant Experiment � Identified seven pairs of contrasting alleles among garden peas: › › › › Seed color (yellow or green) Seed shape (smooth or wrinkled) Pod color (yellow or green) Pod shape (inflated or pinched) Flower color (purple or white) Flower position (axial or terminal) Stem height (tall or short)

Parts of a Flower Image acquired from http: //www. chesterfield. k 12. sc. us/cheraw%20 intermediate/Dave. Evans/Biology. ICP/Flower. Parts. jpg

Gregor Mendel Breeding Peas VIDEO - Father of Genetics Gregor Mendel

Gregor Mendel Pea Plant Observations Noticed that genes always came in pairs � Every organism receives two alleles for each trait � › One allele from each parent › Alleles were not always equal

Dominant and Recessive Noticed that some traits disappeared in the first generation of hybrids › “Recessive” - Not visible › Appears only if the plant does not have a dominant allele › Must have two recessive alleles � Traits that appear - “Dominant” › Appears if at least one dominant allele is present �

Gregor Mendel Law of Dominance Later generations - recessive traits reappeared in a mathematically predictable pattern › Example: Later generations of plants had one green pea for every three yellow peas; The same ratio appeared for all seven pairs of traits. � Experiments led to the Law of Dominance › An organism receives two genes for each trait, one from each parent. › Expressed genes - dominant › Hidden” gene - recessive � Law of Segregation › States that a parent passes on at random only one allele for each trait to each offspring. �

Gregor Mendel The Father of Genetics 8 years - Grew an estimated 28, 000 pea plants � 1864 - Published the results of his experiment � › › � Proposed theory of heredity Began the formal field of genetics Methods were advanced; results groundbreaking No one realized how his discovery would eventually revolutionize science until 40 years after his death. 1 st scientist to conduct broad, thorough, systematic, and sufficiently rigorous experiments to discern any universal laws governing inheritance.

Gregor Mendel Punnett Squares � A special chart that is used to predict heredity � Geneticists use this tool show all the possible outcomes of a genetic cross and to determine the probability of a particular outcome. VIDEO - Punnett Squares

Heterozygous Homozygous Genotype Phenotype Alleles

Activity: Predicting the Results of Genetic Crosses Objectives: � Make predictions using models of genetic crosses. � Accurately use the terms dominant, recessive, homozygous, heterozygous, genotype and phenotype. � Create Punnett squares using the data provided.

Question How can the possible results of genetic crosses be predicted?

VIDEO - Greatest Discoveries in Genetics

Standard: 2. Life Science Grade Level Expectation: Eighth Grade Concepts and skills students master: 2. Organisms reproduce and transmit genetic information (genes) to offspring, which influences individuals’ traits in the next generation Evidence Outcomes 21 st Century Skills and Readiness Competencies Students can: a. Develop, communicate, and justify an evidence-based scientific explanation for how genetic information is passed to the next generation (DOK 1 -3) b. Use direct and indirect observations, evidence, and data to support claims about genetic reproduction and traits of individuals (DOK 1 -3) c. Gather, analyze, and interpret data on transmitting genetic information (DOK 1 -2) d. Use models and diagrams to predict the phenotype and genotype of offspring based on the genotype of the parents (DOK 1 -2) e. Use computer simulations to model and predict phenotype and genotype of offspring based on the genotype of the parents (DOK 1 -2) Inquiry Questions: 1. How are traits passed from one generation to the next? 2. What traits can be passed to the next generation and what traits cannot? 3. How can patterns in the inheritance of traits be used to predict how frequently they appear in offspring? Relevance and Application: 1. There are benefits and risks to genetic engineering such as cloning, genetically modifying organisms, and replacing genes for therapy. 2. Genome sequencing has many potential applications to the field of medicine. Nature of Science: 1. Understand the interconnected nature of math and science by utilizing math in the prediction of future generations. (DOK 2) 2. Recognize that current understanding of genetics has developed over time and become more sophisticated as new technologies have lead to new evidence. (DOK 1) 3. Critically evaluate models used to represent deoxyribonucleic acid (DNA) and genes; identify strengths and weaknesses of these models for representing complex natural phenomena. (DOK 2 -3)