A 56-Year-Old Man Comes to the Office Due to Difficulty

question 58

Multiple Choice

A 56-year-old man comes to the office due to difficulty swallowing for the past several months.  He has the most trouble with solid foods and says, "They seem to get stuck in my throat if I don't chew a lot."  The patient has no chest pain or heartburn and has lost 4.5 kg (10 lb) in the last 3 months.  He has been an avid hunter for many years and frequently cures the meat he eats with sodium nitrite.  Physical examination is unremarkable.  Endoscopy shows an ulcerated mass in the distal third of the esophagus, and biopsy samples are obtained from the mass and adjacent normal mucosa.  Analysis of the samples shows accelerated cytosine deamination of chromosomal DNA in both normal and malignant epithelial cells.  This damage is most likely to be repaired through which of the following enzymatic sequences?

• A)Endonuclease, polymerase, glycosylase, lyase, ligase
• B)Endonuclease, polymerase, lyase, glycosylase, ligase
• C)Glycosylase, endonuclease, lyase, polymerase, ligase
• D)Glycosylase, ligase, lyase, endonuclease, polymerase
• E)Lyase, endonuclease, glycosylase, polymerase, ligase