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5.3.12.D. 3 2011 5.3 Life Science: Life science principles are powerful conceptual tools for making sense of the complexity, diversity, and interconnectedness of life on Earth. Order in natural systems arises in accordance with rules that govern the physical world, and the order of natural systems can be modeled and predicted through the use of mathematics. D. Heredity and Reproduction: Organisms reproduce, develop, and have predictable life cycles. Organisms contain genetic information that influences their traits, and they pass this on to their offspring during reproduction Essential Questions Enduring Understandings Labs, Investigation, and Student Experiences How is genetic information passed through generations? There are predictable patterns of inheritance, and the variation that exists within a species is related to its mode of reproduction (sexual or asexual). 5.3.12.D. 3 Content Statements Sorting and recombination of genes in sexual reproduction result in a great variety of possible gene combinations in the offspring of any two parents. Cumulative Progress Indicators Demonstrate through modeling how the sorting and recombination of genes during sexual reproduction has an effect on variation in offspring (meiosis, fertilization). (5.3.12.D.3) Marshmallow Meiosis Purpose: To investigate how variation arises as a result of meiosis and fertilization in sexually reproducing organisms. Introduction: Meiosis is a special type of cell division that takes place in certain cells of sexually reproducing organisms. It results in the production of four daughter cells called gametes that have half the number of chromosomes than that of the original cell. That is why meiosis is sometimes called REDUCTION DIVISION. Furthermore, the four gametes arising from a single cell are different from each other in their genetic makeup. chromosomes (2N=6,) made from marshmallow and toothpicks. It is suggested to write letters A, B, D, E, F, G on the marshmallows in female parent cell to depict genes present in the genotype of one chromosome. Another parent cell would contain the same number of chromosomes (2N=6) in male parent cell with recessive versions of the same genes: a, b, d, e, f, g. Other letters of alphabet should be written on marshmallows representing genes on other chromosomes. Jelly beans connected by toothpicks represent the centromeres of the chromosomes. At the moment, each chromosome is made up of one chromatid, here is one line of marshmallows connected by the toothpicks. Teacher explains that during S phase of the 1 5.3.12.D. 3 2011 Desired Results Students will be able to… 1. Explain the cell cycle, how it contributes to reproduction and maintenance of the cell and/or organism, and explain where mitosis fits into the cell cycle. 2. Understand the factors that cause cells to reproduce. 3. Be able to describe each phase of mitosis and make a simple labeled drawing of mitosis. Indicate that resulting cells contain an identical copy of genetic information from the parent cell. 4. Explain how the apportioning of cytoplasm to the daughter cells follows mitosis, a nuclear eve nt. 5. Compare and contrast asexual and sexual types of reproduction that occur on the cellular and multicellular organism levels. Understand how asexual reproduction differs from sexual reproduction. Know the advantages and disadvantages of each. 6. Explain through the use of models or diagrams, why sexuallyproduced offspring are not identical to their parents. 7. Describe the events that occur in each meiotic phase. 8. Compare mitosis and meiosis; cite similarities and differences 9. Recognize that during the formation of gametes, or sex cells (meiosis), the number of chromosomes is reduced by one half, so that when fertilization occurs the diploid number is restored. 10. Recognize random mutation (changes in DNA) and events that occur during gamete formation and fertilization (i.e., crossing over, independent assortment and recombination of chromosomes) as the sources of heritable variations that give individuals within a speciessurvival and reproductive advantage or disadvantage over others in the species. 11. Explain why sex-linked traits are expressed more frequently Interphase, chromatids duplicate, now each chromosome consists of two chromatids, or two lines of marshmallows connected by toothpicks and both lines connected by a toothpick via a jellybean, as a centromere. Students will resemble the makeup of the parent cell and proceed with phases of the meiosis now. Four groups of 3-5 students will work on imitating a crossing over in the Prophase I. Students will pair up homologous chromosomes by aligning marshmallows into pairs (homologous chromosomes) and join the jelly beans of each line of marshmallows, thus forming tetrads. Now, students are ready to proceed with imitation of the crossing-over by randomly exchanging the marshmallows blocks with written letters on them between lines of marshmallows that represent non-sister chromatids of homologous chromosomes; thus only letters of the same type can be exchanged: A with a; b with B, etc. Teacher should constantly remind students that this process is random – some letters are exchanged and others are not. The longer the line of marshmallow (the longer the chromatid), the higher the rate of the crossing-over! The Y chromosome is extremely small, and does not undergo crossing-over with the X chromosome. At this moment, teacher asks students to compare the genotype of the cell in the Prophase I with the original parent cell (a teacher’s model). Students should arrive to a conclusion that the crossing-over brings the gene shuffling and as a result the cell in Prophase has a very different genotype from the original parent cell. Next, students imitate the metaphase of the Meiosis I by aligning the pairs of homologous chromosomes on the equator of an imaginary cell. Alignment of pairs of homologous chromosomes on the metaphase plate (an equator) is also random. Teacher stresses out that in Anaphase I there is a random separation of chromosomes from each pair. This random 2 5.3.12.D. 3 2011 in males. 12. Compare and contrast the processes of growth (cell division) and development (differentiation). 13. Recognize that any environmental factor that influences gene expression or alteration in hormonal balance may have an impact on development. 14. List some of the problems in cell division when control is lost. 15. Recognize that cancer is a result of mutations that affect the ability of cells to regulate the cell cycle. 16. Describe early embryonic development and distinguish each: oogenesis, fertilization, cleavage, gastrulation and organ formation. 17. Describe the structure and function of the human male and female reproductive systems. 18. Model a random process (e.g., coin toss) that illustrates which alleles can be passed from parent to offspring. 19. Describe the relationship between DNA, genes, chromosomes, proteins and the genome. 20. Explain that a gene is a section of DNA that directs the synthesis of a specific protein associated with a specific trait in an organism. 21. Use Punnett squares, including dihybrid crosses, and pedigree charts to determine probabilities and patterns of inheritance (i.e. dominant/recessive, co-dominance, autosomal/sex-linkage, multiple-allele inheritance). 22. Analyze a karyotype to determine chromosome numbers and pairs. Compare and contrast normal and abnormal karyotypes. 23. Explain how sex chromosomes inherited from each parent determines the gender of the offspring. separation of chromosomes from the homologous pair represents the independent assortment. At the end of the Anaphase I, one chromosome form each homologous pair is moved to the opposite poles, thus at the end of Telophase I and followed cytokinesis, two daughter cells are formed different form each other and from the parent cell. These cells are haploid (N=3), and they have different genetic makeup – marshmallow lines have a very random letters of upper and low cases: AbDEFg, and aBdefG. Students proceed with the rest of Meiosis II and should end up with four haploid cells, which now would participate in fertilization. Students asked to record the sequence of the letters, representing the genes on each line on a separate index card. Each group will be given 4 ziplock bags of small size for cells that came from the male parent cell, and 4 ziplock bags of really large size for the cells coming from the female parent cell. One card will list letters (genes) that are present on one chromosome. Each ziplock bag would have 3 index cards: 2 cards list the sequence of letters (genes) on the two autosomes and one card will have either X letter or Y letter. Students with the small ziplock bags, representing sperm cells are on the one side of the room, and students with the large ziplock bags, representing egg cells. Teacher stress the fact that small bags (sperm cells have either X chromosome or Y chromosome) and large ziplock bags contain only X chromosomes. Now, teacher explains that fertilization is a random process, and sperm cell with most energy and speed will actually participate in the process. So, students who hold the small bag, are asked to do ten set ups, ten jumps, and run to any student who holds the large bag in order to put cards from the small bag into the large bag, thus representing the randomness of the process. Now students analyze the genotype of the 3 5.3.12.D. 3 2011 fertilized egg. They should see that its genetic makeup is very different from both original parent cells. Teacher repeats that it is due to the random process of the crossing-over and independent assortment, or separation of chromosomes in the anaphase I. 4 5.3.12.D. 3 2011 PERFORMANCE ASSESSMENT “Effect of Coffee on Health” OVERVIEW Coffee is a brewed beverage prepared from roasted seeds, known as coffee beans, of the coffee plant. Due to its caffeine content, coffee can have a stimulating effect in humans. Today, coffee is one of the most popular beverages worldwide. Some scientists conducted an experiment in which they evaluated various measurements of human health in people who drank at least one cup of coffee a day. 5 5.3.12.D. 3 2011 They found no significant differences in the health indicators between the subjects who drank only one cup of coffee a day and those who drank as many as 20 cups a day. They concluded that coffee has no adverse effects on human health. Write your answers to the following in the spaces below. YOUR TASK 1. What were the independent and dependent variables in this experiment? 2. Was this a controlled experiment? If so, what were the control and experimental groups? 3. Do you agree with the conclusion the scientists drew from their results? Why or why not? 6