Dr. Reichlerπs Bio 212 MWF 2-3pm Print Name:____________KEY____________

Exam #3 Nov. 11, 2003

Answer each question as succinctly as possible in the space provided. If needed, continue on the back. If you use a drawing as part of your answer, be sure to also include a written explanation. Read each question carefully and donπt hesitate to ask if a question seems unclear. 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. Each question is worth 6 pts, unless otherwise noted, for a total of 103 points possible for this exam.

1. What is one piece of information that you would need to know about a gene to insert and/or express it in bacteria? How would you use this information to ensure that this gene would be inserted and/or expressed in the bacteria? (8 pts)

Any of: need to know the sequence so that you can choose a restriction enzyme or so PCR primers can be made. Need to know if there are introns so reverse transcription can be done if needed. Need to know about the promoter so that it can be matched with a bacterial promoter for expression.

2. How are restriction enzymes used when inserting a gene into bacteria, and what is one important issue when deciding which restriction enzyme to use?

Restriction enzymes are used to cut the plasmid and the gene of interest. Any one of: needs to not cut inside the gene, should cut in the lacZ gene for blue/white screening, must cut on both sides of the gene, should leave sticky ends for ligation.

3. What role would antibiotics play in transformation of a plant (inserting a gene into plants)?

To transform a plant, first agrobacterium must be transformed. To select successfully transformed agrobacterium, antibiotic resistance can be used.

4. You are given a small sample of plant tissue from two plants of the same species. Plant Z is suspected of being genetically modified, while plant X is known to not be genetically modified. How would you determine whether plant Z had been genetically modified or not? Do not just name the method(s), but also briefly describe what the method(s) entail. (8 pts)

Any of: Use PCR with primers specific for the allegedly inserted gene. Failure or success of PCR will indicate whether the plant has the inserted gene.

Perform RFLP analysis with DNA from both plants. Amplify region of alleged inserted gene, cut with same restriction enzyme and look for same or different pattern of bands.

5. What are one similarity and two differences between genetic engineering and breeding (artificial selection)?

Any one similarity: both modify organisms DNA, both are in common use today, both are used to ≥improve≤ crops.

Any two differences:

Breeding- choose traits, must breed to choose traits, only can use genes already in organism,

Gen Eng- choose gene, genes inserted, can introduce new genes,

6. When genetically modifying a human, what is the greatest danger to the person being genetically modified?

The inserted gene might insert into an existing gene thereby disrupting the function of that gene.

7. Cyclin and CDK, working as MPF, signal the cell to enter mitosis. What two types of cellular proteins does MPF likely signal? Explain. (8 pts)

Any two of: histones (proteins to pack up DNA), cytoskeleton or mitotic spindle proteins, motor proteins (to move chromosomes)

8. Do all tumor cells within one tumor have identical DNA? Why or why not?

No, tumor cells are dividing rapidly, and some replication errors are building up. 4/6 points for yes, they are all derived from one cancer cell.

9. How could information about gene expression help determine whether a cancer was benign or malignant?

Tracking the expression of genes that are involved in cell to cell connections. Poor or incorrect expression of these genes might indicate a malignant tumor.

10. Why is it important for doctors to know whether a cancer is benign or malignant? (8 pts)

Benign tumors are all in one place and can be treated with surgery or radiation. Malignant tumors are possibly spreading and chemotherapy is the only way to kill all cancer cells.

11. Why do organisms that reproduce sexually need to do both meiosis and mitosis?

Meiosis makes haploid gametes that can join with someone elseπs gametes to form a zygote that then uses mitosis to develop into an adult that can perform meiosis making more gametesä

12. If I showed you a cell dividing under a microscope, and I told you that the cell was going through the second division of meiosis, could you be certain whether it was mitosis or the second division of meiosis?

Either: No, in both meiosis 2 and mitosis, sister chromatids line up and separate. OR Yes, in humans there would be 23 sets of sister chromatids in meiosis 2, and 46 sets in mitosis.

13. What advantage does a diploid cell have over a haploid cell?

Diploid cells having 2 sets of each gene can have one gene damaged and the other can compensate.

14. How does sexual reproduction increase genetic diversity?

By combining genetic info from 2 individuals.

15. Is genetic diversity important for a speciesπ survival? Why or why not? (8 pts)

Either: Yes, almost all multicellular organisms reproduce sexually, so it must be important; and in experiments a correlation between environmental stress and sexual reproduction has been demonstrated. OR No, in experiments increasing environmental stress did not necessarily lead to increases in sexual reproduction.

Bonus: How could the likelihood of developing cancer be heritable? (3 pts)

Any of: Excellent or poor DNA repair enzyme genes could be inherited. If someone inherited cells with some mutations, that would increase the likelihood of the several mutations needed for cancer.