Dr. Reichler's Bio 301    Print Name:____________KEY____________

Exam #1   Oct. 1st, 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 donÕt 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 104 points possible for this exam.


1.     Why do we consider life on earth to be carbon-based?

All of the 4 biomolecules (carbohydrates, lipids, amino acids/proteins, and nucleotides) are comprised primarily of carbon.


2.     Everything that we consider as being alive has a membrane.  Why is a membrane critical to being considered alive?

Living organisms must be organized.  Membranes help organize the cell by separating inside from outside.


3.     Why is recognition of the intron/exon border critical for proper protein production?

Improper splicing of the intron would change the reading frame of the exons.


4.     What gene would be expressed in all human cells?  Why would this gene be expressed in all human cells?  (8 pts)

Many answers, only one is needed:  Histones-all cells have DNA that needs to be packaged, RNA polymerase- all cells are transcribing, tRNA or ribosomes-all cells are translating,


5.     What gene would be expressed only in some human cells, and what type of cell (by name or description) would be expressing this gene?  Explain.  (8 pts)

Many answers, only one is needed:  DNA polymerase-only cells replicating the DNA need this protein, telomerase-only cells going through a lot of mitosis/DNA replication need this,


6.     What are one similarity and two differences between the leading and lagging strand of DNA replication?

Similar:  any one of- both need primer to start.  Both go 5Õ-3Õ, both use DNA polymerase, each origin of replaication has two leading and two lagging strands,

Different:  any two of- leading is toward unwinding, lagging moves away from unwinding; lagging uses many primers, leading only one primer; leading strand is continuous, lagging strand is in small pieces,


7.     During DNA replication, what is happening to the hydrogen bonds and covalent bonds on both the original (template) and new DNA strand?

Original strand is breaking hydrogen bonds and nothing is happening to the covalent bonds.  New strand is forming both hydrogen bonds and covalent bonds.


8.     How are replication errors detected and repaired?

Mismatched DNA is detected by the distortion of the 3-D structure of the double helix.  The incorrect DNA is removed and the correct bases are put in.


9.     What prevents a cell with short telomeres from performing mitosis?  (8 pts)

This cell cannot replicate its DNA and therefore cannot perform mitosis.


10.  If you were watching a cell undergo mitosis, how would you know when mitosis had ended?

Either the cell would divide, and/or, the DNA unpackages, and/or, the nucleus reforms


11.  What protein might be over-produced or over-abundant in a cancer cell?  Why?

Any one of:  Telomerase- to maintain long telomeres so the cell can continue to replicate the DNA and divide; MDR- to efflux toxins


12.  Why did your Mom provide slightly more than 50% of your DNA?

Mitochondria have DNA and the mitochondria are inherited maternally


13.  How could we determine whether humans from Africa and from Europe are the same species?

If they can reproduce and their offspring can reproduce, then they are the same species.  So if they are sharing genetic info, they are the same species


14.  Why do people who have been separated for a long time have more differences in their mitochondrial DNA than people who have been separated recently?

More time apart leads to more mutations and more differences in the mtDNA.


15.  Formulate a question about cancer.  Then apply rules 1 and 2 of Strong Inference (the parts prior to actually doing any experiments) to answer your question.  (10 pts)

A question with at least two hypotheses about this question plus at least one experiment that can disprove one or more of the hypotheses.

Example:  Q- what causes cancer?  HypoÕs- radiation.  DNA replication.  Water.  Expt- expose humans to water and radiation and see which ones develop cancer.




Bonus:  What is problematic about using mitochondrial DNA to study human ancestry?  What was the solution to this problem that Dr. Sykes used?  (4 pts)

mtDNA only traces maternal lineage.  It only traces female migration.  By looking at the Y chromosome, which is only inherited via males, he could look at male lineage and male migration.