Dr. Reichler’s Bio 301L   MWF 9-10am    Print Name:____________KEY_______
Exam #1   September 27, 2006

    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. Apply rules 1 and 2 of Strong Inference (the parts prior to actually doing any experiments) to answer the following question:  How do cells maintain membrane fluidity in cold temperatures? (8pts)
Must use Strong Inference and make multiple hypotheses and experiments to eliminate hypotheses.  Ex:  hypo’s- Cells change from saturated to unsaturated lipids.  Cells add choloesterol.  Cells no not change the lipids.  Expt- Lower the temperature and measure ratio of saturated and unsaturated lipids before and after cold temperature.

2. Explain how using controls and doing statistical analysis relates to Strong Inference. (4pts)
Rule three of Strong Inference states that we need reliable results if we are to eliminate the correct hypotheses.  Using statistics and doing controls is part of getting reliable results.

3. Phosphorous has 15 protons.  Would a radioactive phosphorous atom decay into silicon with 14 protons or sulfur with 16 protons?  Why? (8pts)
Sulfur, an electron leaves from one of the neutrons from phosphorous and that neutron becomes a proton making the 16 protons which is sulfur.

4. What two characteristics of lipids make them effective in forming barriers? (4pts)
A hydrophilic, water soluble head, and a hydrophobic, water insoluble tail.

5. How are carbohydrates used differently in plant and animal cells? (4pts)
Any one of:  The plant cell wall is carbohydrates while the animal Extracellular matrix is protein.  Plants produce carbohydrates in the chloroplast while animal cells must take in carbohydrates from the environment.

6. How could you determine what climate a plant lived in based on the lipids in its membrane? (8pts)
Plants from a colder climate should have more unsaturated lipids, while a plant from a warmer climate should have more saturated lipids.

7. Transposons are examples of genes acting as replicating units.  Relate transposons to two other gene definitions. (8pts)
Any two of:
Genes code for proteins- some transposons make transposase, a protein, that is involved in moving the DNA.
Genes are units of heredity- transposons are inherited from the parents.
Genes cause diseases- when a transposon disrupts another gene, that can cause a disease by disrupting the normal function of the gene product.
Genes are switches- transposons can disrupt genes thereby disrupting normal development.

8. If a transposon moved once from one part of your DNA to another part, is it likely to cause a problem?  Why or why not? (8pts)
No, most of our DNA is non-coding, so the chance of damage to a gene is low.
6/8 pts  Yes, If the transposon inserts into a gene, it would disrupt the proper coding of the protein made from that gene.

9. What are two parts of a cell where you would find RNA?  What is it doing in each place? (8pts)
Any two of:  Nucleus- being transcribed.  Cytoplasm- being translated.  Endoplasmic reticulum- being translated into a membrane protein.  Cytoplasm- as rRNA (ribosome) or tRNA.

10. A nucleotide is changed in the coding region of the gene that codes for transposase, but the transposase protein still functions properly.  How is this possible? (8pts)
Redundancy in the genetic code means that some nucleotides can be changes, but still code for the same amino acid.

11. Most multicellular organisms are diploid.  What is one disadvantage to being haploid? (8pts)
Any one of:  There is no other copy of the genes.  So if there is any problem or mutation, there is only the one copy that is now damaged.
Haploid organisms cannot reproduce sexually thereby limiting genetic diversity.

12. A woman has a mutation on her mitochondrial DNA that causes a protein to not be produced, and that causes her to have low energy levels.  Her husband does not have this mutation.  Will their offspring have low or normal energy levels?  Why? (8pts)
All children will have low energy.  MtDNA is inherited only from mom.  Dad will not pass on any of his MtDNA.

13. You are breeding kittens, and you want kittens with short tails.  One gene controls tail length with long tails being dominant and short tails recessive.  Mom is heterozygous and the dad is homozygous recessive.  What percent of the kittens will have short tails? (8pts)
50%.  Mom is Tt.  Dad is tt.  Possible offspring Tt, Tt, tt, tt.

14. Male humans inherit less DNA from their fathers than their mothers.  Give two reasons why this is true. (8pts)
MtDNA is maternally inherited.  The Y chromosme is smaller than the X chromosome, and males inherit the X from mom and the Y from dad.

Bonus:  If DNA does not directly cause diseases, what does? (3pts)
Proteins or RNA that are improperly produced.