BSCI 420, 421, BIOL 620 CELL BIOLOGY Fall 2001

Exam I

Name: ____________KEY__________________

Course Section: (Please circle)

420, 421 Tues lab, Wed lab, Thurs lab, 620

Check to see that you have 8 pages, including this one.

You have one hour to complete the exam.

Please write clearly and in pen if you want a regrade.

Good luck.

Multiple Choice

1. ______ of 27 points

Short Answer

2. ______ of 18 points

3. _____ of 16 points

Experimental Design

4 ______ of 20 points

Essay. Write on one of these two

5 ______ of 20 points

6. ______ of 20 points

 

Total _101__ of 101 points

 

 

 

 

BSCI. 421, 420, 620 Name ____________________________

Exam I, Fall 2001

(27) 1. Multiple choice: (circle the number of the one best choice):

  1. The first living cells are thought to have arisen about
    1. 4.5 billion years ago.
    2. 3.5 billion years ago.
    3. 4.5 million years ago.
    4. 3.5 million years ago.

b) The feature that most clearly separates eukaryotes from prokaryotes is the presence in eukaryotic cells of

    1. ribosomes.
    2. Oxidative phosphorylation.
    3. DNA molecules.
    4. A nucleus.

c) What is the evolutionary relationship between the present day eubacteria, archaebacteria, and eukaryotes deduced from DNA sequencing?

1) Eubacteria and archaebacteria are more closely related to each other than to eukaryotes.

2) Archaebacteria and eukaryotes are more closely related to each other than to eubacteria.

3) Eubacteria and eukaryotes are more closely related to each other than to archaebacteria.

4) Genes for nuclear functions are more closely related to archaebacterial genes and genes for cytosolic and plasma membrane functions are more closely related to eubacterial genes. (We’ll accept either or both 2 & 4)

d) When mitochondria are separated from lysosomes by centrifugation the best method to use is called

1) Differential centrifugation.

2) Velocity centrifugation.

3) Density-gradient centrifugation.

4) Analytical centrifugation.

 

e) Restriction nucleases are enzymes that

1) Act only in a single species of bacteria

2) Act only on the ends of DNA strands

3) Cleave DNA only at specific sequences

4) Cleave only nuclear DNA

f) The first enzymatic step in making a cDNA uses the enzyme

1) EcoR1 nuclease

2) Taq polymerase

3) DNA polymerase

4) RNA-dependent DNA polymerase

g) A poly-A tail is added to a mRNA by

1) RNA polymerase, which reads a string of complementary dTs at the end of the gene.

2) Poly-A polymerase, which adds A’s sequentially to the end of the transcript.

3) Poly-A transferase, which adds a pre-made string of A’s to the end of the transcript.

4) Poly-A correctase, which recognizes an AAUAAA signal at the end of the message and changes the U to an A.

h) Homeodomain genes that determine major patterning in early development bind to DNA via

1) Zinc fingers

2) Helix-loop-helix domains

3) Helix-turn-helix domains

4) Leucine zipper domains

i) Release of RNA polymerase II to initiate transcription appears to be the direct result of:

1) Binding of TFIID to the TATA box.

2) Binding of general transcription factors to the polymerase.

3) Phosphorylation of RNA polymerase by a protein kinase.

    1. Removal of nucleosome(s) occupying the promoter site.

 

 

 

 

 

 

BSCI 421 Name

 

(18) 2. Contrast (What are the important differences between?): (write on two of three)

a) Enhancers and promoters? (Give three differences)

1) An enhancer can be upstream, downstream, or in an intron of the coding region of a gene, whereas a promoter can only act upstream.

2) An enhancer can be a long distance from the gene coding sequence it regulates, but a promoter must be right next to the (start site of the) gene.

3) An enhancer can act in either orientation, but a promoter can only act in one orientation

4) An enhancer can only act through a promoter, but a promoter can act on its own.

    1. An enhancer can have a negative or a positive effect, but a promoter has only a positive effect.

 

b) The tertiary and quaternary structure of a protein?

The tertiary structure is formed by interaction of distant parts of one polypeptide chain.

Quaternary structure is formed by the interaction of two or more individually folded polypeptide chains, each with their own tertiary structure.

(They both involve similar bonds)

 

 
  1. The roles of HSP 70 and HSP 60 in mediating the proper folding of a polypeptide chain into a protein?

Hsp 70 is a molecular chaperone that binds individually to exposed hydrophobic areas of nascent or denatured proteins, then releases with

ATP being split, allowing the protein the opportunity to fold correctly.

Hsp 60 is a polymeric chaperonin that envelops improperly folded polypeptides,

massages them into a different configuration by changing the shape of the barrel-like polymer, then releasing the polypeptide to fold again into (hopefully) the native shape.

  1. 3. Short answer:
  1. a) Given the data in table 3-1, place a filled circle where you expect Transferrin to be located and an open circle where you expect Lysozyme to be located after 2-dimensional gel electrophoresis on the gel below. 1) Horizontal: Isoelectric focusing; 2) vertical:

SDS-PAGE. Assume they are both monomers.

 

 

 

 

 

 

 

 

__________________________________________

500

 

MW 100

(kDa) o

50

o

10 __________________________________________

pH 4 5 6 7 8 9 10

 

(8) b) Diagram the ubiquitin-mediated proteolytic pathway, and label the components like the figure in your text.

 

 

See fig 3-18, p. 67

 

 

 

 

 

 

 

(20) 4. For two of the following four, design experiments and explain how you would support the following conclusions: (Give the essential steps, including the enzymes or primers you would use and the results that you would expect. Remember experiments require a control)

a) The effect of promoters is unidirectional.

 

 

 

 

 

 

 

b) The telomere sequence is coded for by an RNA sequence in the enzyme, telomerase.

 

 

 

 

 

 

 

c) The stimulatory effect of enhancers is inversely proportional to the distance from a promoter (if greater than 400 bp away).

 

 

 

 

 

 

 

 

 

 

d) The CEN, TEL, and ARS sequences are necessary for complete replication and accurate segregation of a chromosome to daughter cells in yeast.

BSCI 421 Name ________________________________

Discussion questions: Write on one of the following two discussion questions 5 or 6 for 20 points.

(Leave blank or X out the one you are not writing on).

(20) 5. Discuss origins of replication. What are they? How many of them are present in a typical human chromosome? How does the replication of DNA start at a eukaryotic origin of replication?

Origins of replication are DNA sequences where replication of DNA begins.

A typical human chromosome has several hundred origins of replication.

Replication of eukaryotic DNA starts by the binding of a protein like the T antigen of SV-40 that recognizes the OR sequence and unwinds it.

Replication factor A proteins (RFAs) bind to the single strands and keep them open.

DNA polymerase alpha (with its primase domain) binds to unwound DNA and makes an RNA primer and then a short stretch of DNA before being stopped and displaced by PCNA.

Then Polymerase delta binds to PCNA and begins synthesis of the leading stand from the short segment made earlier.

Polymerase alpha now makes more Okazaki fragments from the lagging strand and replication is started.

BSCI 420, 421, 620 Name ______________________________

(20) 6. Discuss telomeres. What are they? How and when are they put on chromosomes? What are the functions of telomeres?