4. In 1928, English microbiologist Frederic Griffith demonstrated that DNA is the genetic material to determine the virulence of bacteria cells; what observations helped this conclusion?
(A) The heat-killed pathogenic bacteria + live non-pathogenic bacteria -＞ pathogenic.
(B) The heat-killed non-pathogenic bacteria+ live pathogenic bacteria -＞ pathogenic.
(C) The transformation of bacteria was carried by a heat-stable genetic material.
(D) The heat-treated bacteria protein is pathogenic
(E) Pathogenicity reflects the action of the capsule gene.

50 Which of the following best describes the tone of the passage? (A) Pessimistic. (B) Suggestive. (C) Cynical. (D) Neutral.

1. According to the fluid mosaic model of cell membranes, phospholipids _____ (A) have hydrophilic tails in the exterior of the membrane (B) frequently flip-flop from one side of the membrane to the other (C) occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane (D) can move laterally along the plane of the membrane (E) can be rearranged during membrane fusion.

2. The genetic code is essentially the same for all organisms. From this, what can be assumed? (A) The same codons in different organisms translate into different amino acids. (B) A gene from an organism can theoretically be expressed by any other organism. (C) Different organisms have different types of amino acids. (D) DNA was the first genetic material. (E) The abundance of all tRNAs are the same in different organism.

3. Which of the following contradicts the one-gene, one-enzyme hypothesis? (A) Alkaptonuria results when individuals lack a single enzyme involved in the catalysis of homogentisic acid. (B) Sickle-cell anemia results in defective hemoglobin. (C) A mutation in a single gene can result in a defective protein. (D) A single antibody gene can code for different related proteins, depending on the splicing that takes place post-transcriptionally. (E) Human insulin is encoded by one gene and processed after translation into two conjugated polypeptides for its active form.

5. What is the mechanism of information transfer in eukaryotes? (A) Messenger RNA is transcribed from a single gene and transfers information from the DNA in the nucleus to the cytoplasm, where protein synthesis takes place. (B) Transfer RNA takes information from DNA directly to a ribosome, where protein synthesis takes place. (C) DNA from a single gene is replicated and transferred to the cytoplasm, where it serves as a template for protein synthesis. (D) Proteins transfer information from the nucleus to the ribosome, where protein synthesis takes place. (E) Retrovirus-mediated gene transfer can only occur prenatally during pregnancy

6. Which of the following occurs in prokaryotes but not in eukaryotes? (A) post-transcriptional splicing (B) translation in the absence of a ribosome (C) concurrent transcription and translation (D) gene regulation (E) alanine can be added to polypeptide chain by tRNA with different codons

7. A ribozyme is  _____.(A) a catalyst that uses RNA as a substrate (B) an enzyme that synthesizes RNA as part of the transcription process (C) an enzyme that catalyzes the association between the large and small ribosomal subunits (D) an RNA with catalytic activity (E) an important component of RNA transport from nucleus to cytoplasm.

8. A mutant bacterial cell has a defective aminoacyl-tRNA synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that _____.(A) the positions of phenylalanine in proteins will still encode phenylalanine (B) the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons (C) the cell is not able to synthesize lysine (D) the ribosome will skip a codon every time a UUU is encountered (E) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU

9. A mutation that inactivates a regulatory gene of a repressible operon in an E. coli cell would result in _____.(A) continuous transcription of the structural gene controlled by that regulator (B) irreversible binding of the repressor to the operator (C) complete inhibition of transcription of the structural gene controlled by that regulator (D) continuous translation of the mRNA because of alteration of its structure (E) defects in cell division

10. The primary difference between enhancers and promoter-proximal elements is that enhancers _____.(A) enhance transcription; promoter-proximal elements inhibit transcription (B) are transcription factors; promoter-proximal elements are DNA sequences (C) are at considerable distances from the promoter; promoter-proximal elements are close to the promoter (D) are DNA sequences; promoter-proximal elements are also DNA sequences (E) are only identified in eukaryotic cells but not in prokaryotic cells.