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SAMPLE QUESTIONS

1.  Which of the following cell compartments is associated with a protein skeleton composed of lamins? 
(A) Chloroplast    (B) Basement membrane  (C) Mitochondrion   (D) Nucleus 
(E) Peroxisome

2.  A previously unknown organism that lacks a nuclear membrane and mitochondria has just  been discovered. Which of the following would this organism most likely possess? 
(A) Lysosomes  (B) Cilia  (C) Ribosomes  (D) Endoplasmic reticulum  (E) Chloroplasts 

3. Drugs that either stabilize or depolymerize microtubules can be used in cancer chemo- therapy. Which of the following is correct concerning such drugs? 
(A)  They stimulate the immune system.  (B) They prevent chromatin condensation. 
(C)  They prevent movement of tumor cells  into other tissues. 
(D)  They interfere with mitosis.    (E)  They interfere with endocytosis.

4.  Initiation of mitogenesis by epidermal growth factor and depolarization of the membrane of a skeletal muscle cell by acetylcholine are similar in that each 
(A)  involves, as an essential early step, an ion flux across the plasma-membrane receptor of the responding cell 
(B)  requires a ligand-mediated conformational change in a plasma-membrane receptor of 
the responding cell  
(C)  requires activation of a G  protein on the cytoplasmic face of the plasma membrane 
in the responding cell 
(D)  is mediated by phosphorylation of the ligand receptor in the responding cell 
(E)  completes its primary task by direct activation of specific regulatory DNA sequences in the nucleus of the responding cell

5. SNARE proteins are found in the membranes  of all of the following compartments EXCEPT 
(A) Mitochondria (B) Golgi complex (C) Early endosome (D) Endoplasmic reticulum 
(E) Synaptic plasma membrane

6. Membrane carrier proteins differ from membrane channel proteins by which of the following characteristics? 
(A)  Carrier proteins are glycoproteins, while channel proteins are lipoproteins. 
(B)  Carrier proteins transport molecules down their electrochemical gradient, while channel proteins transport molecules against their electrochemical gradient. 
(C)  Carrier proteins can mediate active transport, while channel proteins cannot. 
(D)  Carrier proteins do not bind to the material transported, while channel proteins do. 
(E)  Carrier proteins are synthesized on free cytoplasmic ribosomes, while channel proteins are synthesized on ribosomes  bound to the endoplasmic reticulum.

7. Eukaryotic cells with DNA damage often cease progression through the cell cycle until the damage  is repaired. This type of control over the cell cycle  is referred to as 
(A) proteosome control (B) damage control (C) checkpoint control (D) anticyclin control 
(E) transcriptional control

8. Cytokinesis in animal cells is caused by 
(A)  the sliding movements of a band of microtubules around the circumference  of the cell 
(B)  the contraction of a band of actin filaments around the circumference of the cell 
(C)  the movement of the mitotic spindle fibers 
(D)  endocytosis of the plasma membrane around the equator of the cell 
(E)  fusion of cytoplasmic membrane vesicles at the equator of the cell

9. The synthesis of mRNA’s that encode the proteins of eukaryotic ribosomes occurs in the 
(A) cytoplasm (B) nuclear envelope (C) nucleolus (D) euchromatin (E) heterochromatin

10. Which of the following best describes the hyperchromicity of DNA? 
(A)  The shift in UV absorbance to longer wavelengths upon denaturation 
(B)  The shift in UV absorbance to shorter wavelengths upon hydrolysis 
(C)  The shift in UV absorbance to longer wavelengths upon annealing (forming double strands) 
(D)  The increase in absorbance at 260 nm upon annealing 
(E)  The increase in absorbance at 260 nm upon Denaturation

11. The karyotype of a triploid plant contains 72 chromosomes. How many chromosomes  would the karyotype of a diploid plant of the  same species contain? 
(A) 24   (B) 48   (C) 49   (D) 71  (E) 96

12. The DNA from the bacteriophage  X174 has a base composition of 25% A, 33% T, 24% G, and 18% C. Which of the following best explains this observation? 
(A)  In viral genomes, the base pairing does not follow the standard Watson-Crick rules, and allows G-A and C-T base pairs. 
(B)  In viral genomes, the base pairing does not follow the standard Watson-Crick rules, and allows G-T and C-A base pairs. 
(C)  Viral genomes are linear and tolerate base-pair mismatches. 
(D)  Nucleic acids from viruses are tightly complexed with nucleic acid-binding proteins and so cannot base-pair with one another. 
(E) The genome of bacteriophage  X174 is single-stranded.

13. Consider the average in vivo turnover rates for proteins,DNA, and mRNA. Which of the following orders best describes the turnover rate from fastest (shortest average lifetime) to slowest (longest average lifetime)? 
(A)  mRNA  >  DNA  >  proteins     (B)  mRNA  >  proteins  >  DNA 
(C)  Proteins  >  mRNA  >  DNA     (D)  Proteins  >  DNA  >  mRNA 
(E)  DNA  >  mRNA  >  proteins

14. When the nucleus of a frog red blood cell,  which does not replicate DNA, is transplanted into an enucleated frog egg, the egg goes through several cell divisions. Which of the following is the best interpretation for this phenomenon? 
(A)  Isolated red-blood-cell nuclei  synthesize DNA. 
(B)  The nucleus plays no role in cell  division. 
(C)  An enucleated frog egg can divide. 
(D)  Genes do not function during early  cleavage. 
(E)  The cytoplasm controls nuclear DNA synthesis.

15. Which of the following statements about repetitive DNA is NOT true? 
(A)  Repetitive DNA is associated with the centromeres and telomeres in higher eukaryotes. 
(B)  Repetitive DNA is restricted to nontranscribed regions of the genome. 
(C)  Repetitive DNA sequences are often found in tandem clusters throughout the genome. 
(D)  Repetitive DNA was first detected because of its rapid reassociation kinetics. 
(E)  Transposable elements can contribute to the repetitive DNA fraction.

16.  Mitosis and meiosis accomplish segregation of the replicated DNA to two or more daughter cells. Which of the following is characteristic of both mitosis and meiosis? 
(A)  Chromosomes attach to spindle fibers composed of actin. 
(B)  The resulting cells are diploid (2n). 
(C)  The resulting cells are haploid (1n). 
(D)  Spindle fibers attach to chromosomes at their kinetochores. 
(E)   Chiasmata form between chromosome arms.

17. All of the following processes occur in  the pathway leading to regulated protein  secretion in animal cells EXCEPT 
(A)  formation of transport vesicles from  the rough endoplasmic reticulum 
(B)  an increase in the concentration of cytosolic calcium ions prior to secretion 
(C)  synthesis of an amino-terminal signal sequence 
(D)  phosphorylation of a mannose residue  in a glycoprotein 
(E)   trimming of N-linked oligosaccharides

18.  All of the following statements about the  fluid mosaic model of biological membranes  are true EXCEPT: 
(A)  Lipid molecules in the membrane readily undergo lateral diffusion. 
(B)  Lipid molecules in the membrane readily undergo transverse (flip-flop) diffusion. 
(C)  Integral membrane proteins can undergo lateral diffusion. 
(D)  The saturated hydrocarbon chains of lipid molecules in the membrane undergo 
carbon-carbon bond rotation. 
(E)  The transition temperature of a membrane  is sensitive to the composition of the  
lipid molecules in the membrane.

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