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- 2. 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.
- 3. The passing on of traits from parents to offspring
- 4. The basic unit of inheritance by which characteristics are passed from one generation to the next.
- 5. 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 - Gregor Mendel and Pea Plants VIDEO The Life of Gregor Mendel (23 minutes)
- 6. Why are some traits found in the parents showing up in their offspring, while other traits are not?
- 7. › The different forms a gene may have for a trait › A variation of a gene
- 8. 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)
- 9. Image acquired from http://www.chesterfield.k12.sc.us/cheraw%20intermediate/DaveEvans/BiologyICP/FlowerParts.jpg
- 10. VIDEO - Father of Genetics Gregor Mendel
- 11. 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
- 12. 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
- 13. 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.
- 14. 8 years - Grew an estimated 28,000 pea plants 1864 - Published the results of his experiment › Proposed the 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. 1st scientist to conduct broad, thorough, systematic, and sufficiently rigorous experiments to discern any universal laws governing inheritance.
- 15. 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
- 17. 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.
- 18. How can the possible results of genetic crosses be predicted?
- 19. VIDEO - Greatest Discoveries in Genetics
- 20. 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 21st 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)
Editor's Notes
- #11: Pea plants reproduce when sex cells called gametes join together. Male gametes, or sperm, are produced in pollen grains formed in the stamen. Female gametes, or eggs, are produced in the carpel. During pollination, pollen grains from a male reproductive organ are transferred to a female reproductive organ. There, the male gamete unites with the female gamete in a process called fertilization. The zygote, or the cell that results, then develops into a seed. For two years, Mendel grew different varieties of peas to make sure that their offspring were always the same. Then he began breeding different varieties together to make hybrids. In pea plants, both male and female reproductive organs are located in the same flower. They are tightly protected by the flower petals. Pollen from other flowers is therefore unable to enter a flower on a different plant. Pollination that occurs within a single flower is known as self-pollination. If Mendel wanted two different plants to reproduce, he could open the petals of a flower to remove the male reproductive organs, and then brush pollen from a different plant onto the female reproductive organ. This process is known as cross-pollination. What was so important about being able to cross different plants? By choosing which plants reproduced, Mendel could study how specific traits are inherited, or passed along. He then grew generation after generation of hybrids and tracked the inheritance of the traits.