Final: Biochem Genetics & Cell Cycle End of Chapter Questions

Question 1

A nt sequence 5’-TCCGAT-3’ within human genomic DNA underwent spontaneous mutation resulting in nt sub, producing 5’-TTCGAT-3’. Which one of the following chem rxns could account for the nt sub above?

Answer 1

B. deamination of a pyrimidine

Question 2

Which of the following characteristics of nucleosomes is important for their ability to package genomic DNA into chromatin?

Answer 2

A. histone constituents of nucleosomes contain a relatively high proportion of lysine and arginine amino acids.

Question 3

which of the following observations is evidence for semiconservative DNA replication?

Answer 3

C. After DNA synthesis, each daughter molecule contains one parental strand and one new strand

Question 4

The following DNA sequence is the template for synthesis of newly transcribed RNA: 5’-GGGAAAT-3’. Which of the following sequences represents the RNA synthesized from the template?

Answer 4

A. 5’-AUUUCCC-3’

Question 5

The anticancer drug cytarabine can be metabolically activated into the compound shown below. Which of the following enzymes is inhibited by this compound?

Answer 5

A. DNA polymerase delta

Question 6

One mechanism of potential mutation is the insertion of an incorrect nt by DNA pol delta and epsilon into the newly synthesized DNA molecule. Which of the following enzymes, present at the replication fork, repairs nt disincorporation by DNA pol delta during DNA synthesis?

Answer 6

D. DNA polymerase delta

Question 7

The PEPCK-C gene is transcribed in the liver under normal conditions, and its transcription is induced significantly by glucocorticoids. It was reported in the literature that a nt 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?

Answer 7

C. silencer element

This was the question thrown out on the last test.

Question 8

p16 is a member of the INK family of CDK inhibitor proteins (CIP). It functions by binding to CDK4 and CDK6. What effect does the action of p16 have on the cell cycle?

Answer 8

C. p16 blocks passage of cell cycle thru restriction pt in late G1

Question 9

Strain of bacteria resistant to antibiotic was isolated in hospital lab. Biochem analysis show treatment of sensitive strain w/antibiotic blocks bacterial RNA synthesis, whereas resistant strain, RNA synthesis was unaffected. The resistant strain is unaffected by which of the following drugs?

Answer 9

C. Rifampcin

Question 10

What effect does damage to DNA have on p53 protein?

Answer 10

B. stabilizes p53; DNA damage triggers phosphorylation and release of p53 from ubiquitin ligase

Question 11

Which event is characteristic of intrinsic and extrinsic apoptosis?

Answer 11

D. activation of caspases 3, 6, and 7

Question 12

How do genetic mutations in proto-oncogenes contribute to cancer?

Answer 12

A. They alter the structure or amount of gene’s protein product

Question 13

Which of the DNA sequences would have greatest thermal stability?

Answer 13

E. CCCGGGA; greatest # G-C pairs

Question 14

Valproic acid is clinically used to treat seizures. Biochemically, it is an inhibitor of histone deactylases. Treating cells with valproic acid will likely alter the charge of which of the following amino acids in histones?

Answer 14

E. Lysine

Question 15

Cells from pt that cannot produce GlcNAc phosphotransferase (phosphorylates mannose on asparagine-linked oligosaccharide chains) would be unable to transport newly synthesized glycoporteins to which of the following locations?

Answer 15

B. Lysosomes

Question 16

The DNA translocation generating the Philadelphia chromosome involves which proto-oncogene and is diagnostic for which disease?

Answer 16

D. ABL tyrosine kinase, chronic myelogenous leukemia

Question 17

During the elongation phase of prokaryotic translation, for each amino acid added to the growing peptide chain, 2 FTP molecules are hydrolyzed to GDP. Which of the following aspects of ribosome function requires hydrolysis of one GTP?

Answer 17

B. Aminoacyl-tRNA delivery to A site

on last test

Question 18

The mRNA sequence 5’-GCG ACG UCC-3’, is being translated by a ribosome. Which of the following sequences represents anticodons of aminoacyl-tRNAs that used (in order) during translation?

Answer 18

D. 5’-CGC, CGU, GGA-3’

Question 19

Which of the following antibiotics will inhibit cytoplasmic protein synthesis in both prokaryotic and eukaryotic organisms?

Answer 19

E. Puromycin

Question 20

You are cloning BamHI-cut genomic DNA into the plasmid vector pBR322, which has both ampicillin resistance gene and a tetracycline resistance gene. If the inserts are ligated into the BamH1 site in the tetracycline resistance gene vector, the entire population of transformed bacteria should first be grown on

Answer 20

B. media containing ampicillin

Question 21

When ribosome reaches stop codon on mRNA, release factors act to change specificity of peptidyl transferase so that the growing peptide chain is transferred to which of the following moieties?

Answer 21

A. Water

on last test

Question 22

Recombinant human granulocyte-macrophage growth factor (GMCSF), a hematopoietic factor used to treat neutropenia, can be produced in a human cell line engineered to synthesize the protein. Analysis of the glycosulation 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 8 carb oligosaccharide. Which of the following is true regarding the glycosylated rGMCSF?

Answer 22

D. The oligosaccharide is attached to rGMCSF via an acid amide functional group

Question 23

IF you are screening a library by nucleic acid sequence homology with a radio labeled DNA probe, how are the bacterial colonies of interest identified?

Answer 23

B. X-ray film

Question 24

Sometimes the gene responsible for a particular genetic disease has not yet been cloned, so researchers must use a probe that is genetically linked to the gene they wish to follow. If a new restriction fragment length polymorphism (RFLP) is detected using a probe linked to the gene, this result may be interpreted to mean ..?

Answer 24

C. that a mutation has occurred in the gene or in the region flanking the gene

Question 25

A 34yo 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 particular sensitive?

Answer 25

C. Medical X-rays

Question 26

A 31yo man emigrated from Vietnam and recently returned from a visit to his home country presents to office w/CC of sore throat, fever, and malaise. Exam observe gray membrane covering tonsils and pharynx. Find never been vaccinated for diphtheria. In cells exposed to the toxin, which of the following processes related to gene expression are affected as a direct result of action of toxin?

Answer 26

E. Transcriptional elongation

Question 27

The public health department recently reported isolation of tetracycline-resistant strain of Treponema palladium in your area. Biochem analysis determined that resistance associated w/change in ribosome structure that alters ribosome function. Which of the following functions in protein synthesis is most likely to be altered in strain?

Answer 27

C. Binding of aminoacyl-tRNAs to the A site

Question 28

You must evaluate the genetic status of a family with 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?

Answer 28

C. Variable number of tandem repeat (VNTR) analysis

Question 29

A couple w/child affect with CF requests genetic test, mom preggers. Genetic status of fetus desired. PCR amplification test for mutation responsible for 70% of all CF and obtained data diagrammed below. What do you tell the family?

Answer 29

A. fetus does not carry gene

Question 30

The following table lists the GC content of the genomes of several pathogenic bacteria. Based on difference in thermal stability of an organism’s genome, which of the following pairs of organisms would be suitable candidates for developing a PCR-based clinical lab assay that would allow the amplification of DNA from one pathogen but not the other?

Answer 30

D. F philomiragia and B. mallei

biggest difference in % G-C content

Question 31

44yo woman emigrated from Poland 3 years ago. In office CC fatigue 6months. Previous doc= anemic and prescribed oral iron supplements, which she stopped taking because of taste. Exam was unremarkable. Coversation, revealed mother died from colon cancer at 51 and maternal grandfather at 55. Lab tests indicate she was indeed anemic, and a fetal occult blood test was positive. On follow-up, colonoscopy and following pathologic exam of biopsied lesions resulted in colon adenoma with villous features. Genetic testing indicated that the woman has a mutation resulting in a defect of a DNA repair pathway. Which of the following pathways is most likely dysfunctional in this patient?

Answer 31

B. Mismatch excision repair

Question 32

Physician exploring best treatment for 56yo pt diagnosed with breast cancer. To show that his pt may be good candidate for Herceptin, he plans to exam a biopsy of her cancerous tissue for expression levels of which of the following proteins?

Answer 32

B. HER2/NEU family of receptors

Question 33

2yo male pt brought in by mom, son’s left eye had glow similar to that of a cat’s eye caught in headlights. She also notices that eyes appeared crossed, and he appears to have diminished vision in his left eye. The physician sends the child to an ophthalmologist, who confirms that the child has tumors in his retina. What is most likely cause of this pt’s condition?

Answer 33

D. a “loss of function” mutation in the RB gene

Question 34

A novel pharmaceutical agent in development claims to inhibit the activity of CDK2. The effect of this agent on cell cycle should include…?

Answer 34

A. inhibition of the G1/S transition

Question 35

You carry out an experiment in which human brain RNA is analyzed via hybridization to a DNA probe. Which of the following best describes the hybridization technique used in this experiment?

Answer 35

C. Northern blotting

Question 36

You wish to clone the gene encoding a peptide hormone that will permit medical students to go without sleep while they are studying for their medical board examinations. You plan to express this gene in bacteria so that the hormone can be purified in commercial quantities. You have an antibody that recognizes the peptide hormone. Wht kind of recombinant DNA library will you screen?

Answer 36

B. cDNA library cloned into an expression vector

Question 37

While working in medical mission in Honduras, a 7yo child brought to you by parents. Parents tell you that child has always had “very bad skin and been very sick” whenever they can afford, they take boy to hospital in nearest city for treatment of skin lesions. While child was infant, docs told parents he cannot ever be exposed to sunlight,. Exam, find significant number patches discolored skin with areas of blistering of face, arms, and neck are oozing and raw (xeroderma pigmentosum). Molecular analysis of DNA from boy’s skin keratinocytes would reveal an abundance of which of the following types of lesions?

Answer 37

B. Pyrimidine dimers

Question 38

Recent report identified G-C transversion in gene encoding for hematopoietic transcription factor GATA1 in genome of pt with congenital syndrome Diamond-Blackfan anemia. Deletion caused a loss of exon 2 in transcribed mRNA. Biochem analysis of cells homozygous for mutation indicated no functional GATA1 protein was produced. What is the likely nucleotide substitution in GATA1 genes of patient?

Answer 38

C. splice donor site

Question 39

child born from consanguineous parents has congenital defect in pituitary development. Genetic analysis revealed a 5 nt deletion associated w/child’s PIT1 genes that was associated with significantly diminished levels of PIT1 mRNA. PIT1 genes activity is required for normal pituitary development. Biochem analysis of cells biopsied from child determined that acetylation of chromatin associated with the PIT1 core promoter was significantly lower than in matched cells from healthy donor. The 5 nt deletion is likely in which of the following elements associated with the PIT1 gene?

Answer 39

A. enhancer

Question 40

26yo woman comes in for check up. wants babies. currently on patch: low does synthetic estrogen and progesterone and will discontinue its use immediately. Both of rugs activate gene transcription through mechanism similar to another steroid family, glucocorticoids. At genes that are activated by estrogen, what changes in histone modification will likely occur in short term (hours to days) once the woman discontinues her use of contraceptive patch?

Answer 40

A. decreased acetylation