Dr. Reichler’s Bio 212  1-2pm        Print Name:______KEY____________ (2 pts)
Final Exam  December 11, 2002

    This exam is optional.  This exam will replace your lowest test grade whether this grade is higher or lower than your previous lowest grade.  If you have any questions about this, ASK.  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 don’t 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 100 points possible for this exam.

1. According to Strong Inference, what are the advantages of using disproof rather than proof?
Proof can be misleading, but once something is false it is always false.

2. The RNA world hypothesis states that RNA was the first living molecule.  Would life have continued to evolve if this RNA molecule was able to replicate itself without any errors?  Explain.
No, mutations/ errors are needed for new alleles to form.  The replicating RNA would not have improved or changed without mutations.

3. a.  Describe or name four genes that must be expressed for a cell to complete the cell cycle?  For each describe why it is critical for the completion of the cell cycle.  (8 pts)
Any four of:  Many possible answers for genes involved in DNA replication, transcriptiuon, translation, etc.

b. A protein called “keepitmoving” is translated at high levels during mitosis.  Why is this unexpected, and how might this be possible?
There is generally not much gene expression during mitosis because the DNA is tightly packaged into chromosomes.  If this mRNA was made prior to mitosis, it can be translated during mitosis.

4. a.  Telomerase is not expressed in most adult human cells, but it is commonly found in cancer cells.  Why do cancer cells need telomerase?
Cancer cells are constantly replicating the DNA and dividing the cell.  Each DNA replication causes a gap/ a loss of some DNA from the ends of the DNA.  Telomerase elongates the DNA, keeping critical info/ genes from being lost.

b. Telomerase expression in cancer cells is due to a mutation in the telomerase gene.  In what part of the telomerase gene would you expect to find the mutation?  Explain.
Any of:  Change to promoter so that more transcription occurs, Change to UTR so that mRNA is more stable, Change protein sequence so protein is not degraded

5. a.  Describe the function of two parts of a gene that are not transcribed into mRNA.  (4 pts)
Any two of:
Promoter- where and when of transcription.  Terminator- stop of transcription.  Introns- function unknown.

b. Describe the function of two parts of an mRNA that are not translated into protein.  (4 pts)
Any two of:
Introns- function unknown.  5’ untranslated region (UTR)- ribosomes bind, mRNA stability.  3’ UTR- mRNA stability.  G-cap- ribosomes bind, mRNA stability.  Poly-A tail- mRNA stability.

c. What nucleotide substitution (the replacement of one nucleotide with another) would be disastrous for the production of a protein?  Explain.
Any of:  Change start codon- translation will never occur.  Change stop codon- translation will not stop properly, and protein will have many extra amino acids.

6. a.  Why is PCR (Polymerase Chain Reaction) important for genetic engineering?
PCR is used to isolate and amplify the gene of interest from the organisms DNA.

b. What effect might genetic engineering of a plant have on the evolution of the plant species?
Any of:  It introduces new alleles or genes like a mutation would.  It could affect the evolution, by giving some plants a selective advantage.

7. After gametes fuse during sexual reproduction, all of the genetic information is present.  How are different cell types produced from this single cell?
Via mitosis and differential gene expression.
 
8. a.  Would the mutant allele for over-expression of a positive cell cycle regulator (a signal to continue the cell cycle) be a dominant or recessive allele?
Dominant.  The gene is being over-expressed, so it does not matter if the normal allele is present, the gene will still be over-expressed.

b. How is genetic diversity increased during meiosis?
Via independent assortment and crossing-over/recombination

9. Imagine that you work for the government, and you are in charge of dispersing $1 billion for research in biology.  Towards what one area of research would you give the money?  What is the scientific basis for your decision?
Various answers.  Reasons must be based on science.

10. Using rules 1 and 2 of Strong Inference, the parts prior to doing an experiment, answer the following question:  What is the purpose of the “extra” DNA (the 90% that does not code for genes) in humans cells?  (10 pts)
Various answers.  This answer must include multiple hypotheses, and an experiment designed to eliminate one of the hypotheses.
Example:  Hypo’s-  Has no purpose.  Has a purpose.  Expt.  Remove extra DNA from a human cell.  See if it is normal or not.