Book Questions Flashcards
A nucleotide sequence 5’-TCCGAT-3’ within human genomic DNA underwent spontaneous mutation resulting in a nucleotide substitution, producing the sequence 5’-TTCGAT-3’. Which one of the following chemical reactions could account for the nucleotide substitution above?
A. Conversion of a deoxyribosyl group to a ribosyl group
B. Deamination of a pyrimidine
C. Hydrolysis of the N-glycosidic bond in a purine
D. Hydrolysis of a phosphodiester bond
E. Methylation of a cytosine
B. Deamination of a pyrimidine
One mechanism of potential mutation is the insertion of an incorrect nucleotide by DNA polymerases delta and epsilon into the newly synthesized DNA molecule. Which of the following enzymes, present at the replication fork, repairs nucleotide misincorporation by DNA polymerase delta during DNA synthesis?
A. DNA ligase B. DNA helicase C. DNA topoisomerase D. DNA polymerase delta E. DNA polymerase alpha
D. DNA polymerase delta
DNA pol delta has 3’->5’ exonuclease activity, DNA pol alpha does the primer
The PEPCK-C gene is transcribed in the liver under normal conditions, and its transcription is induced significantly by glucocorticoids. It was reported in literature that a nucleotide substitution, at a position outside the protein coding region of the PEPCK-C gene, resulted in consistently elevated levels of PEPCK-C transcription that were only increased slightly by glucocorticoid treatment. Which of the following regulatory elements is most likely the site of this mutation?
A. Core promoter B. Enhancer element C. Silencer element D. Transcriptional start site E. Polyadenylation site
C. Silencer element
A strain of bacteria resistant to a specific antibiotic was isolated in a hospital lab. Biochemical analysis demonstrated that treatment of the sensitive strain with the antibiotic resulted in a block in bacterial RNA synthesis, whereas in the resistant strain, RNA synthesis was unaffected. The resistant strain is unaffected by which of the following drugs?
A. Chloramphenicol B. Tetracycline C. Rifampicin D. Acyclovir E. Amoxicillin
C. Rifampicin
Valproic acid is a drug used clinically to treat seizures. Biochemically, it is an inhibitor of histone deacetylases. Treating cells with valproic acid will likely alter the charge of which of the following amino acids in histones?
A. Aspartate B. Glutamate C. Histidine D. Arginine E. Lysine
E. Lysine
Histones are rich in the basic amino acids arginine and lysine. Acetylation occurs only on the positively charged e-amino acid groups of lysine residues. This neutralizes the basic charge and reduces the affinity of DNA for nucleosomes, making it more accesible to the transcriptional machinery
During the elongation phase of prokaryotic translation, for each amino acid added to the growing peptide chain, 2 GTP molecules are hydrolyzed to GDP. Which of the following aspects of ribosome function require the hydrolysis of one of these GTP molecules?
A. Peptide bond formation
B. Aminoacyl-tRNA delivery to A site
C. Binding of CAP-binding complex to the 7-methyl-guanosine cap of mRNA
D. Assembly of the small and large ribosomal subunits
B. Aminoacyl-tRNA delivery to A site
You are cloning Bam HI-cut genomic DNA into the plasmid vector pBR322, which has both an ampicillin resistance gene and a tetracycline resistance gene. If the inserts are ligated into the Bam HI site in the tetracycline resistance gene of the vector, the entire population of transformed bacteria should first be grown on
A. media containing no antibiotic
B. media containing ampicillin
C. media containing tetracycline
D. media containing both ampicillin and tetracycline
B. media containing ampicillin
Because a genomic DNA insert will inactivate the tetracycline resistance gene, the transformants must be grown on ampicillin. This will select against any bacterial cells that were not transformed by a plasmid
When the ribosome reaches a stop codon on mRNA, release factors act to change the specificity of peptidyl transferase so that the growing peptide chain is transferred to which of the following moeities?
A. Water B. eIF4F C. Formyl-methionine D. UDP-GlcNAc E. The E site
A. Water
Release factors interact with peptidyl transferase, allowing it to transfer the nascent polypeptide chain to water instead of to the alpha-amino group of an incoming aminoacyl tRNA
Recombinant human granulocyte-macrophage growth factor (GMCSF), a hematopoeitic gactor used to treat neutropenia, can be produced in a human cell line engineered to synthesize the protein. Analysis of the glycosylation of recombinant GMCSF (rGMCSF) was performed with PNGase F, an enzyme that catalyzes the complete removal of N-linked oligosaccharides from proteins at the site of attachment. Treatment of rGMCSF released an eight carbohydrate oligosaccharide. Which of the following is true regarding the glycosylated rGMCSF?
A. The oligosaccharide is attached to rGMCSF at an amino acid that can also serve as a site for phosphorylation
B. The oligosaccharide is attached to rGMCSF via a mechanism that is insensitive to tunicamycin treatment
C. The oligosaccharide is attached to rGMCSF via a hydroxyl functional group
D. The oligosaccharide is attached to rGMCSF via an acid amide functional group
E. The oligosaccharide is attached to rGMCSF via a mechanism that does not require dolichol phosphate
D. The oligosaccharide is attached to rGMCSF via an acid amide functional group
N-linked glycosylation of arginine residues is via an acid amide (CONH2) functional group
If you are screening a library by nucleic acid sequence homology with a radiolabeled DNA probe, how are the bacterial colonies of interest identified?
A. Microscope
B. X-ray film
C. Scintillation counter
D. Culture techniques
B. X-ray film
A 34-year-old woman whose mother died from breast cancer and whose sister was recently diagnosed with the disease comes to you for genetic testing. The results of the tests indicate she has a homozygous mutation in her BRCA1 genes. To which types of DNA damaging agents will this woman be particularly sensitive?
A. Alkylating agents B. Intercalating agents C. Medical X-rays D. Sunlight E. Adduct forming agents (e.g., benzo(a)pyrene)
C. Medical X-rays
BRCA1 codes for a protein involved in the homologous recombination repair pathway. This pathway is particularly important in repairing double-stranded breaks in the DNA. Ionizing radiation, such as X-rays, are capable of producing double-stranded breaks (among other types of damage)
The public health department in your state recently reported the isolation of a tetracycline-resistant strain of Treponema pallidum in your area. Biochemical analysis has determined that the resistance is associated with a change in ribosome structure, which alters the ribosome’s function. Which of the following functions in protein synthesis is most likely to be altered in the tetracycline-resistant strain of T. pallidum?
A. Assembly of the 30S pre-initiation complex
B. Entry of the 50S ribosomal subunit to create the initiation complex
C. Binding of aminoacyl-tRNAs to the A site
D. Peptidyl transferase activity of the 70S ribosome
E. Translocation of the 70S ribosome
C. Binding of the aminoacyl-tRNAs to the A site
You must evaluate the genetic status of a family with a history of Huntington disease and wish to determine the number of triplet repeats in each individual. What would be the best way to estimate the number of triplet repeats?
A. Real-time PCR
B. cDNA library construction
C. Variable number of tandem repeat (VNTR) analysis
D. RFLP analysis
C. Variable number of tandem repeat (VNTR) analysis
A novel pharmaceutical agent in development claims to inhibit the activity of CDK2. The effect of this agent on the cell cycle should include:
A. Inhibition of the G1/S transition
B. Maintenance of RB in a hyperphosphorylated state
C. Inhibition of the CDK inhibitor proteins p21 and p27
D. Promotion of the transcription of genes for cyclin E and cyclin A
A. Inhibition of the G1/S transition
