Deck 4: Nucleic Acid Extraction Methods

Question 1

DNA, after separation from other cellular constituents, is precipitated in which of the following?

A) Chloroform
B) Isopropanol
C) Ethylenediaminetetraacetic acid
D) Sodium dodecyl sulfate

Answer 1

Isopropanol

Question 2

In organic DNA extraction methods, the DNA is found in which fraction?

A) Upper aqueous
B) Lower aqueous
C) Upper hydrophobic
D) Lower hydrophobic

Answer 2

Upper aqueous

Question 3

Which whole blood fraction is the most abundant source of genomic DNA?

A) Red blood cells
B) Buffy coat
C) Serum
D) Plasma

Answer 3

Buffy coat

Question 4

What is the concentration of DNA whereby a 1:100 dilution has an absorbance reading of 0.015 at 260 nm?

A) 6 g/mL
B) 60 g/mL
C) 75 g/mL
D) 750 g/mL

Question 5

Which of the following is the first step in DNA isolation from cells in a clinical sample?

A) DNA precipitation
B) Precipitation of proteins
C) Lysis of cells
D) Eluting DNA from a spin column

Question 6

Which fixative is the least damaging to nucleic acids?

A) B5
B) Bouin's
C) All mercury-based fixatives
D) Buffered formalin

Question 7

DNA is isolated from a clinical sample. The absorbance at 260 nm is 0.489, and the absorbance at 280 nm is 0.257. Is this sample of sufficient quality for use in subsequent analyses?

A) Yes
B) No
C) Cannot be determined with the data given

Question 8

In inorganic DNA isolation, or "salting out" procedures, in the presence of low-pH and high-salt concentrations, which intracellular component precipitates out of solution?

A) DNA
B) RNA
C) Carbohydrate
D) Protein

Question 9

Nucleic acid concentration can be assessed relatively simply and quickly by which of the following procedures?

A) Electrophoresis
B) Enzyme immunoassay
C) Sequencing
D) Spectrophotometry at 260 nm

Question 10

What is the concentration of RNA whereby a 1:10 dilution has an absorbance reading of 0.675 at 260 nm?

A) 33.75 g/mL
B) 337.5 g/mL
C) 27 g/mL
D) 270 g/mL

Question 11

Phenol/chloroform and an aqueous solution will form what type of mixture?

A) Simple solution
B) Emulsion
C) Suspension
D) Supersaturated solution

Question 12

What is the yield of RNA from the sample with concentration of 450 g/mL and a volume of 0.3 mL?

A) 135 g
B) 150 g
C) 225 g
D) 450 g

Question 13

Which of the following will yield the best DNA preparation?

A) Fixed tissue
B) Hemolyzed blood
C) Fresh blood
D) Stool

Question 14

In organic isolation of RNA procedures, guanidinium isothiocyanate is added to:

A) Degrade DNA
B) Denature all proteins
C) Inhibit RNAses
D) Separate RNA from DNA

Question 15

Which of the following is used to optimize yield of nucleic acid by precipitation or column purification?

A) Carrier molecules
B) Detergent
C) Tris buffer
D) Isotonic saline

Question 16

Diethyl pyrocarbonate (DEPC) is a chemical that is used to:

A) Inactivate DNAses
B) Measure DNA concentration
C) Isolate mitochondria
D) Inactivate RNAses

Question 17

What is the yield of DNA from a sample with concentration of 280 g/mL and a volume of 0.5 mL?

A) 70 g
B) 140 g
C) 280 g
D) 560 g

Question 18

The most abundant form of RNA in all cells is:

A) Ribosomal
B) Transfer
C) Messenger
D) Small nuclear

Question 19

PolyT oligomers bound to a matrix resin column will selectively isolate which of the following?

A) Ribosomal RNA
B) GC-rich DNA
C) Transfer RNA
D) Messenger RNA

Question 20

Which of the following will not inhibit RNAses?

A) Guanidine isothiocyanate (GITC)
B) Tris buffer
C) Strong reducing agents
D) High-salt buffers

Question 21

In what way is fluorometry more accurate than spectrophotometry?

A) Fluorescence is more specific for single nucleotides.
B) Spectrophotometry only measures absorbance from intact nucleic acid polymers.
C) Using specific stains, fluorometry only detects intact double-stranded DNA.
D) Absorbance may require dilution of sample before reading.

Question 22

The 260 nm/280 nm ratio for isolated DNA was determined to be 1:2. What should be done next with this sample?

A) Proceed with DNA analysis as necessary.
B) Reprecipitate the DNA to remove excess protein.
C) Treat the sample with RNAse to remove RNA.
D) Dilute the sample to 1:10 and repeat spectrophotometry.

Question 23

Isolated DNA has an absorbance at 260 nm of 0.268 and an absorbance at 280 nm of 0.191. What is the 260 nm/280 nm ratio?

A) 1:2
B) 1:4
C) 1:6
D) 1:8

Question 24

A DNA-specific dye that is used in fluorometry procedures to measure DNA concentration is:

A) Ethidium bromide
B) Diethyl pyrocarbonate
C) SYBR Green
D) Hoechst 33258

Question 25

When measuring the concentration of RNA by spectrophotometry at 260 nm, the absorbance reading is multiplied by the dilution and a conversion factor of:

A) 20
B) 30
C) 40
D) 50