1. We watched a video called "Burden of Knowledge." This video discussed how having more knowledge about a given situation may not always be the best thing. Explain how having the results of an amniotic test may be beneficial in some circumstances and how it might be deleterious in other circumstances. 15 points
2. Using B and b, give the likely genotype of the individuals in the figure at the right: (6 points)
3. What is meant by genotype and phenotype? (4 points) Which of these did Mendel study? (1 point)
Genotype is the set of genes an organism possesses.
Phenotype is the set of measurable or recognizable traits that result from the genotype.
Mendel studied phenotype.
4. Give an example of a trait that does not follow Mendel's laws and explain why it does not. (5 points)
several examples are possible but they follow one of the following (only one answer needed):
· multigenic/polygenic traits that are the result of many genes contributing to the trait - such as height, shape of nose, etc.
· incomplete dominance is the result of each allele making a product that contributes to the observed trait so that if only one allele is present, the trait is incomplete - such as in flowers that are red because they have two "red" alleles. If only one allele is present, half as much red pigment is made and the flower is pink
· codominance results when each allele is expressed and that expression does not have an influence on the other allele. An example is the ABO blood types - each allele can make either A antigen, or B antigen, or no antigen. Red blood cells can therefore be AA, AB, AO, BB, BO, or OO.
· sex linked traits are associated with gender - not a Mendelian inheritance
5. In what way does the quality of ear wax relate to incidence of breast cancer? Explain your answer. (6 points)
Wet ear wax leads to a higher incidence of breast cancer than does dry ear was. Ear wax is produced by the apocrine gland system which includes the mammary glands as well. Apparently, the different alleles in the apocrine gland system that lead to ear wax "quality" also influence susceptibility to breast cancer.
6. Describe what a centromere is and how it functions during mitosis. (6 points)
The centromere is the structure that holds sister chromatids together after the DNA has been replicated. It is used to help align the chromosomes along the metaphase plate, and after the centromere is cleaved, allows the chromosomes to be pulled towards the poles of the cell by the spindle fibers.
7. What happens during S-phase of the cell cycle? (2 points)
The cellular DNA is replicated.
8. Explain the process of crossing over during meiosis. Why is it important? (3 points)
Crossing over is a process in which corresponding parts of chromosome pairs can swap genetic information by having their DNAs cut and reconnected. It is important because it leads to more genetic diversity.
9. What are the roles of growth and differentiation during development? (6 points)
Growth is the process of cell division which allows the developing embryo to become larger, including all of its component organs. Differentiation is the process of cells becoming more specialized and acquiring the ability to perform specific tasks unique to that particular cell type.
10. Describe one function of the voltage gradient across the cell membrane. (3 points)
There are several, including (but not limited to): conduct signal (action potential) down a nerve cell, force molecules across membrane, provide energy to "pumps" that transport molecules, provide a defense mechanism to some organisms (electric eel).
11. Describe two different membrane bound organelles inside eukaryotic cells and explain their cellular roles. (6 point)
many organelles: nucleus (contains genetic information, chromosomes), mitochondria (responsible for energy production from food), chloroplasts (responsible for photosynthesis), endoplasmic reticulum (involved in protein synthesis and processing, steroid biosynthesis), Golgi apparatus (modification of proteins), lysosomes (contain digestive enzymes and can digest food)
12. Explain how force is generated by actin-myosin interaction. You may use a labeled diagram if you wish. (4 points)
Myosin molecules have little "arms" on them which stick out from the myosin at an angle. The ends of these arms interact with an actin molecule. Using the energy in ATP, the myosin arms bend and move the actin molecule. The arm is then reset and ATP drives another cycle of bending to continue moving the actin. This movement produces a force at the ends of the actin and myosin molecules.
13. Cancer cells are immortal. Explain what is meant by this statement. (3 points)
Normal cells can be placed in a Petri dish and allowed to grow and divide. After a fixed number of divisions (usually 50-100), these cells will be unable to divide any further - thus the cells are "mortal". On the other hand, cancer cells can keep dividing indefinitely and so are said to be immortal.
14. Describe an experiment that was done to demonstrate that DNA is the genetic material. (5 points)
We discussed two: (1) R and S pneumonia bacteria; S is lethal to mice, R is not. Heat killing S makes them non-lethal. Mixing heat killed S with R, and then injecting into mice is lethal. The R strain picked up something form the cell debris of the killed S strain. Treating the killed S with DNAase eliminated the "transforming" ability of the extract, but proteinase did not - the "transforming principle" therefore had to be DNA. (2) Label phage with either radioactive DNA or radioactive protein. Infect bacteria. Radioactive DNA is injected into the host cell but radioactive protein is not. Radioactive DNA is found in progeny phage but radioactive protein is not.
15. In chromatin, DNA only represents about 1/3 of the mass. What components make up the remaining 2/3? (2 points)
Of the remaining 2/3, 50% is histone and 50% is non-histone proteins
16. Diagram and label how s-factor functions in prokaryotic transcription. (5 points)
17. DNA repair enzymes can recognize mismatched bases in newly synthesized DNA. Explain how the enzymes know which of the two bases needs to be replaced. (4 points)
Once the mismatch is detected, the repair enzyme determines which is the original DNA strand (with the correct base) by looking at the extent of methylation on each DNA strand. The older strand will by methylated, while the newly synthesized strand will not be.
18. Some single stranded RNA phage contain several coding regions on a single polycistronic mRNA, yet immediately after infection only the first coding region is expressed. Slightly later on, additional coding regions are translated. How does this happen? (5 points)
The first start codon is available when the RNA enters the cell and is therefore translated. Other start codons are not available initially because they are involved in base-pairing to other regions on the RNA. During translation of the first gene region, the ribosomes disrupt the previously base-paired regions making their start codons available. These newly available start codons will be recognized and utilized.
19. In order to test the effects of two 
different antibiotics on protein synthesis, you set up three testubes to carry out protein synthesis, which you measure. No antibiotic is added to tube A, antibiotic B is added in tube B, and antibiotic C is added in tube C. From the graphs shown here, explain whether B and C are acting during the elongation or initiation step of protein synthesis. (6 points)
C: translation stops immediately so no additional protein synthesis occurs (no more
amino acids are added to proteins). This is only possible if elongation is blocked
B: in this case, there is not an immediate cessation of protein synthesis. Since more
protein synthesis continues to occur (additional amino acids are added to proteins),
but gradually tapers off, this indicates that elongation continues until the protein is
finished but no more initiation can occur. So B blocks initiation.