|A. Read pages 275-278 and answer Questions pages 283-284: 7-9. Due 14 April.
Terms & Concepts: Understand that meiosis is a specialized form of cell division that produces daughter cells with half the number of usual chromosomes (eg gametes). That is the chromosome number is reduced from diploid (2N) to haploid (1N). Appreciate why this is necessary in sexually reproducing organisms. Use the diagram on pages 276-277 to learn the steps of meiosis, especially the first division cycle. As with mitosis, be able to describe the major events that take place in each stage of meiosis. Also be able to compare the events of meiosis to the corresponding events in mitosis, especially prophase I through telophase I of meiosis. Understand what a tetrad is and how they form from the pairing of homologous chromosomes. Appreciate that the formation of tetrads leads to the "crossing over" of chromosomes and the rearrangement of genes on the chromosomes. This has important implications for the rate of evolution. Use the diagram on page 278 to see the difference in gamete formation between males and females.
B. Read pages 263-266 and answer Questions pages 283-284: 1, 2, 4 and Worksheet #2: Monohybrid Cross problems 1-3. Due 16 April.
Terms & Concepts: Appreciate that genetics is the study not only of how inherited traits pass from one generation to the next, but also an important element in understanding how evolution has shaped the biodiversity of the biosphere. Be aware of the basic historical information concerning Gregor Mendel's life and work. Understand that much of his ground breaking work was possible because he opted to study garden peas rather than some other organism. Know what is means to be a true breeding plant (or animal) and its significance to Mendel's experiments. Use the diagrams on the bottom of pages 264-265 to follow the classic experiments of Mendel that led to his conclusions regarding dominance. Understand the concept of dominant and recessive traits refers to different versions of the same genecalled alleles. Be sure you the clearly distinguish between the terms gene and allele. Understand the significance of the independent segregation of alleles and how the experiment on the bottom of page 265 led Mendel to this conclusion. You have learned about meiosis and the production of haploid gametes. Be sure you can relate Mendel's law of segregation to the events of meiosis.
C. Read the article, "... Tomatoes Look Great But Taste Bland" from the Discover Magazine blog Not Exactly Rocket Science and answer the following questions. Due 17 April.
D. Read pages 267-269 and answer Questions pages 283-284: 3, 5, 12, 24 and Worksheet #2: Monohybrid Cross problems 4, 5. Due 29 April.
Terms & Concepts: Review the basic rules of probability from your math classes. Understand that probability is a fundamental tool for the analysis of classical Mendelian genetics. Be able to set up a Punnett Square and use it to predict the results of a genetic cross or analyze the results of a genetic cross to determine the genotypes of the parents and progeny. It is especially important that you distinguish between the genotype and phenotype of an individual. Know that the terms homozygous and heterozygous refer to genotypes not phenotypes. Most important, understand that the results of a Punnett Square are predictions of the results of a genetic cross, not the actual results. In other words, the Punnett Square is a hypothesis to be tested against the actual results of the cross.
E. Read pages 270-274 and answer Questions pages 283-284: 6, 14-16, 25, 27 and Worksheet #2: Dihybrid Cross problems 1-3. Due 1 May.
Terms & Concepts: Realize that the results of Mendel's two-factor crosses with pea plants demonstrated that the genes for different inherited traits are passed on to the next generation independently of one another; ie independent assortment. Be able to set up and complete simple two-factors (or dihybrid) crosses using the Punnett Square technique. You will see later on that there are many exceptions to this rule. Appreciate that there are a number of situations that are more complicated than Mendel's experiments. Be familiar with incomplete dominance (common in the color of flowers). Distinguish this from codominance which is common in the hair color of horses and rodents. Finally be familiar with multiple alleles and polygenic traits. These are actually much more common than the simple examples that Mendel studied. Don't be mislead into thinking that genes have total control over the phenotype;. The environment interacts with the genotype in many important ways to produce the final phenotype.
Terms & Concepts: Compare the observation of Mendel that different traits assort independently from one another and those of Morgan that showed some traits seem to be inherited together. Be able to explain why this gene linkage takes place despite the fact that chromosomes do assort independently. Understand how the occurrence of gene linkage changes the predictions of the Punnett Square. Also appreciate that linked genes have been used as a tool by geneticists to create gene linkage maps that show the location of genes along the length of a chromosome. See the diagram on page 280 for an examples of a gene map for the fruit fly, Drosophila.