Dr. Reichler’s Bio 301L   MWF 11am-noon    Print Name:__KEY___________________
Exam #2   March 30, 2007

    Read each question carefully and don’t hesitate to ask if a question seems unclear.  If possible, answer each question in the space provided, but if needed, continue on the back.  If you use a drawing as part of your answer, be sure to also include a written explanation. These questions have specific answers, although for some, more than one answer is possible.  To receive full credit you must clearly and fully answer the question being asked.  This exam is worth 103 points with the points for each question noted in parentheses.

1. What are two processes that occur in a person’s body and/or cells that diminish the risk of cancer, and how does each one diminish the risk of cancer? (8pts)
Any two of:  Shorter telomeres reduce the risk of cancer by keeping cells with mutations via DNA replication or DNA damage from continuing to reproduce.  T-cells recognize abnormal cells, such as cancer cells, and destroy them.  DNA repair will limit the number of mutations.

2. What would happen outside a B-cell, that would not occur to another type of cell, which would cause the B-cell’s telomeres to get shorter? What happens and why does this cause the B-cell’s telomeres to get shorter? (8pts)
The B-cell would recognize its antigen and then begin to divide.  DNA replication that precedes mitosis causes shorter telomeres.

3. After mitosis what are two potential differences between the DNA in the two progeny cells and the DNA in the original cell? (8pts)
Any two of:  The telomeres would be shorter.  There may be mutations/replication errors.  Different packaging.

4. Would you expect the affects of smoking on fetal development to be reversible?  Why or why not? (6pts)
No, development is primarily a one-way street.  The packaged DNA cannot generally be unpackaged.

5. Regarding human ancestors sexual reproduction, what can we infer about physical competition between males and sperm competition?  What evidence leads to these conclusions? (8pts)
Based on the small differences in sizes between men and women it would appear that there was little physical competition between men.  Based on the relative medium testicle size, it would appear there was some sperm competition.

6. Were male or female pipefish choosier about their mates?  Explain. (6pts)
Males were choosier.  While all different size males were able to reproduce, only smaller females were able to reproduce.

7. How can a trait exist in males that is disadvantageous for the male’s survival? (6pts)
If the trait is necessary for reproduction, only males with this trait will pass on their genes.

8. What would be one similarly and one difference in the reaction of the specific immune system to bacteria and viruses? (8pts)
Similarity- B-cells recognize and antibodies mark both bacteria and viruses that are outside cells.
Difference- T-cells help protect against viruses by killing infected cells.  T-cells do not help protect against bacteria.

9. How do dead cells help protect us from bacteria pathogens? (6pts)
The dead cells on the surface of our skin are not easy for bacteria to eat, there is little water, and the cells constantly fall off.

10. To prevent cervical cancer, why is it necessary to be vaccinated against HPV before exposure to the HPV virus? (6pts)
The vaccine causes memory B-cells to be produced that can eliminate the HPV virus before it has a chance to infect cells.  Once HPV infects cells, it can enter the lysogenic cycle and remain dormant.

11. If being infected with a virus increases someone’s risk of cancer, what do we know about that virus?  Explain. (6pts)
It enters the lysogenic cycle.  Only lysogenic viruses can alter a cell’s DNA leading to mutations that might cause cancer.

12. Explain how someone’s risk of cancer can be explained by both nature and nurture. (8pts)
Nature- DNA repair may be more or less efficient in different people.  OR  Some people may be born with some mutations already.  OR  Someon’s T-cells may not recognize cancer cells.
Nurture- Exposure to mutagens, chemicals or viruses, etc, could cause mutations increasing the risk of cancer.  OR  Damage to the immune system’s T-cells could decrease the ability to kill cancer cells.

13. What gene might be differently packaged between a normal cell and a cancer cell?  What is the gene, how is it packaged differently, and why is it differently packaged? (8pts)
Any of:  MDR- unpackaged, some cancer cells are resistant to toxins because of the over-abundance of MDR.  Telomerase- unpackaged, to continue to divide the cancer cells must be elongating their telomeres.  Contact Inhibition- packaged, cancer cells lack contact inhibition so these genes will not be expressed.

14. Based on the fact that normally healthy individuals were most affected by the Spanish flu of 1918, were the differences between the Spanish flu and other flu viruses on the inside or outside of the virus?  Explain. (8pts)
The differences must be on the exterior of the virus.  The Spanish flu was deadly because of an extreme immune reaction.  The immune system recognizes the exterior of the virus.


Bonus:  Would a virus that killed its victims in one day or a virus that killed its victims over a week be more evolutionary successful?  Why?  (3 pts)
The longer the virus takes to kill someone the more individuals it can infect and therefore it will be more successful at passing on its genetic material.