Dr. Reichlerıs Bio 212          MW 9-10am               Print Name:___________KEY____________

Exam #3   April 14, 2004


            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 donıt 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.     If you wanted to express a human telomerase protein in bacteria, what human cells would you use as your source material, why would you use these cells, and how would you prepare the human gene for expression in bacteria?  (8pts)

Gametes or cells undergoing constant cell division such as skin or cancer.  These cells are expressing the gene, so mRNA is available for use with reverse transcription to get the cDNA, the coding region without introns.



2.     What role do restriction enzymes play during genetic engineering of bacteria, and what special characteristic of restriction enzymes makes inserting a gene into bacteria easier?

Restriction enzymes are used to cut the plasmid and the gene of interest.  If the restriction enzymes cut unequally leaving sticky ends/overhangs, then ligating the gene of interest and the plasmid will be much easier due to the base pairing of the complementary sticky ends?



3.     If all of the bacteria that you have been genetically engineering grow with a blue color, what has occurred and what has not occurred?  Explain.

The plasmid has been successfully inserted, only bacteria with plasmid can grow on antibiotic, but no gene has been inserted into the lacZ gene, functional lacZ uses X-gal to make a blue color.



4.     With the planting of more genetically modified crops, what will be the effect on the use of herbicides in agriculture?  Why?

Any of:  They will increase, most genetically modified crops are herbicide resistant so the use of herbicides may increase.  They will decrease, use of herbicide resistant crops will allow farmers to treat their crops more selectively and therefore use less herbicides.



5.     What are one similarity and one difference between genetic engineering of plants and animals?

Any one of:  Similar- use other ³organism² to actually insert genes, can not control where DNA inserts, may use RT/PCR before inserted into plant or animal


Plants- Use Agrobacteria, Can be applied directly to plant,

Animals- Use viruses, Cells to be engineered are removed first,



6.     Why is it important to have some non-gene DNA at the ends of chromosomes?

So that during DNA replication, when some DNA is lost, genes are not damaged.



7.     What protein could you suppress to stop a cell from successfully completing mitosis?  Why would the suppression of this protein stop mitosis?  (8pts)

Any of:  Cyclin or CDK- needed to form MPF, Microtubules- without their formation DNA cannot move, DNA polymerase, Helicase, Primase, or Ligase- without successful DNA replication no mitosis



8.     If you were using a microscope to watch a cell undergo mitosis, how would you know when mitosis had ended?

Any of:  DNA decondenses, cells divide, nucleus reforms



9.     Why are malignant cancers more dangerous than benign cancers, and how would treatment of malignant and benign cancers differ?

Malignant cancer spread from the original tumor.  Benign cancers can be treated with surgery or radiation while malignant cancers must be treated with chemotherapy.



10.  Why is cancer more likely in adults than in children?

Either:  Adult cells have been through more cell division and so have accumulated more replication errors.  OR  Adults, living longer, have been exposed to more environmental mutatgens.



11.  Without examining their DNA, how could you tell whether an individual was haploid or diploid?

Any of:  They reproduce sexually.  Go through Meiosis.



12.  How could you determine whether a person had the same or different alleles for their gene coding for growth hormone?

Use PCR, design specific primers for each allele.  If both amplify, both alleles are present.  If only one amplifies, only one is present.  OR  Genetically- cross them with someone with known alleles, and check a statistically significant number of offspring.



13.  A diploid cell of a mustard plant has 5 pairs of chromosomes: =20 telomeres

a.     How many telomeres would be present in a cell immediately preceding mitosis?  (4pts)

40,  2/4 pts 20


b.     How many telomeres would be present in a cell immediately after mitosis?  (4pts)

20,  2/4 pts 10


c.     How many telomeres would be present in a cell immediately after meiosis?  (4pts)

10, 2/4 pts 5


14.  How can a cell with one pair of chromosomes develop genetic diversity during sexual reproduction?

Crossing-over/recombination  OR  random fertilization



15.  How does sexual reproduction protect offspring from harmful mutations?

By combining DNA with someone else, any mutations from one individual are hopefully complemented by the correct DNA from the other parent.




Bonus:  Some cancer treatments arrest cancer cells in the middle of mitosis.  Why would this cause the cancer cells to die?  (3pts)

During mitosis the DNA is tightly packaged and therefore cannot be used to express genes.  Without gene expression, the cell will eventually die.