SUCCESS! in Clinical Laboratory Science - Molecular Diagnostics (26-50) Exam Graded A+

SUCCESS! in Clinical Laboratory Science - Molecular Diagnostics (26-50) Exam Graded A+ For the purpose of diagnosing genetic diseases, what component of whole blood is used for the extraction of DNA? A. Leukocytes B. Plasma C. Platelets D. Red blood cells - answerA. Leukocytes A. Leukocytes are routinely used for extraction of DNA from human blood. Mature red blood cells and platelets have no nuclei. Plasma or serum can be used for detection of viremia, but it is not used for analysis of genetic diseases. Which of the following statements best describes characteristics of RNase? A. It degrades mRNA but not rRNA. B. It is found in large concentrations on hands. C. Its activity can be eliminated by autoclaving. D. Its activity occurs in a limited temperature range between 25 and 65°C. - answerB. It is found in large concentrations on hands. B. The highest concentration of RNase is found on hands; thus, it is imperative that gloves be worn when working with RNA. RNases are ubiquitous and can act at temperatures below freezing (-20°C) and above boiling. For longterm storage, purified RNA is best stored at —70°C or below. RNases plague experiments in which RNA is used. Simple autoclaving does not eliminate RNase activity. To remove RNases, glassware must be pretreated with an RNase inhibitor, such as DEPC, followed by autoclaving; alternatively, baking glassware in a >250°C oven for 4 hours will destroy RNase. To prevent RNA degradation, isolation of RNA should be done using chaotropic agents (e.g., guanidine isothiocyanate) that inhibit RNase activity. When analyzing RNA in a gel, formaldehyde or other agents that denature RNases must be included in the gel. High-quality (i.e., undegraded) RNA will appear as a long smear with two or three distinct areas that correspond to the ribosomal RNA subunits: 28S (-4800 bases), 18S (-1800 bases), and 5.8S (-160 bases), whereas degraded RNA will appear as a smear at the bottom of the gel Which of the following is the least likely inhibitor of PCR? A. Heme B. Sodium heparin C. DEPC (diethylpyrocarbonate) D. EDTA (ethylenediaminetetraacetic acid) - answerD. EDTA (ethylenediaminetetraacetic a