Biology 205. Spring 2005

Possible essay questions for the final.

We will select three at random and then you will select one of the remaining five to answer. Your are expected to be able to develop your answers in a clear way, and of course, in essay form. You may use diagrams to help illuminate your answers.

You may bring a sheet of 8.5" x 11" paper with whatever notes you need to guide you but you must do the actual writing in class. Feel free to discuss the essays with each other and with me before the exam date. Remember that the final is Thursday May 19 at 11:00 to 12:50 in Science 218.

1. In this course we have often dealt with probability reasoning to solve genetics problems. Discuss three examples of how probability reasoning is used, one from each of the following areas. Pedigree studies, Mendelian genetics, gene mapping or understanding protein synthesis. Pick a problem from each of these areas and explain how to solve the problem. Lay out the assumptions needed very carefully and show how to solve the problem. You may select problems from your text, lecture or lab to discuss.

2. Discuss the Hardy Weinberg law of equilibrium. Be sure to discuss the following: why this law was originally developed, how to derive this law, and the role of this law in evolutionary biology. Be sure to list and briefly discuss each of the assumptions of the Hardy Weinberg law. In the assumption about these assumptions be sure to consider how a violated of each assumption might affect a population.

3. What is a mutation and why are mutations important in biology? Elaborate on your answer with examples of the major types of mutations we have discussed in class. For point mutations discuss the effects of such mutations on the phenotype.

4. The term gene is often defined as a region of DNA that influences the phenotype.  Discuss four different types of genes we have examined in this course. Examples you might discuss include transposons, regulatory genes and constitutive genes. Do genes always code for polypeptides? Give an example of a gene that does not code for a polypeptide and yet affects the phenotype.

5.  Compare and contrast the basic chemistry of proteins and nucleic acids. How are they similar and how are they different? What features of proteins make them useful in cells for a wide range of functions? What features of nucleic acids make them well suited to their role as genetic material?  Why are not proteins well suited to be genetic material?

6.  During meiosis crossing over happens during prophase I. Explain what is meant by crossing over and discuss the significance of crossing over for evolution. Discuss with an example the sort of cross one might carry out to calculate the relative distance between two linked loci.

7. Discuss a final project other than your own. What are the main points of the project? Relate the material in a coherent way to the major concepts we have discussed in this course.

8. As part of our discussion of population genetics we discussed single locus two allele population genetics models.  Discuss the graphical approach to stability analysis developed in this course. Analyze the following constant fitness model: W11 = 0.3  W12 =  1.0  W22 = 0.8  Show how to use graphical analysis to determine the equilibria. Explain what is meant when we call an equilibrium stable and explain how to determine which equilibria are stable using this constant fitness model as an example. As a help for this question you might want to use my spreadsheet program to do your calculations.

9. On the planet Munimula, all species have four copies of each chromosome, in other words genes come not in pairs but in groups of four and gametes end up with two copies of genes at each locus. Suppose we make the following cross related to flower color in Munimulan peas:

PPPP x pppp

If you were the Munimulan equivalent of Gregor Mendel, what sort of phenotypic and genotypic ratios in the F1 and F2 of a monohybrid cross would you expect to observe?

Show how you would solve this problem. First show how you get the F1 and then the F2. Carefully explain each step. Would the scientist observe the same ratios as Mendel found on earth? What sorts of ratios would result from a dihybrid cross assuming independent assortment on Munimula? You might consider flower color and plant height as the two traits.

Note: The situation is the same as if Mendel had worked with peas that were tetraploid instead of diploid.

Assume the following:

Principle of Munimulan segregation: Each gamete gets two genes at random from each group of four.

The dominant phenotype is expressed if an individual has at least one dominant allele. The allele P for purple flower color is dominant over the one for white p, the allele T for tall plant is dominant for the allele t for short plant.

For the dihybrid cross, the flower color and height loci are on non-homologous chromosomes.