Nucleic Acid Extraction Methods Quiz

Answer: Semi-Conductive

Isolation of DNA is important in order to analyze the genetic material. Organic isolation uses an organic mixture of phenol and chloroform to remove contaminants. Inorganic isolation or "salting out" does not use the phenol and chloroform but relies on the low pH and high salt concentration to selectively precipitate proteins. Solid phase isolation used a solid matrix to bind the DNA.

Answer: Hydrophilic property

Due to their hydrophilic properties (which means a high affinity for water), nucleic acids get adsorbed onto the solid phase matrix while proteins, lipids and other contaminants, which are hydrophobic (which means not easily adsorbed by water), continue through the column.

Answer: More rapid and effective

Solid phase isolation is a technique for isolating nucleic acids. Instead of using aqueous substances to retrieve the genetic material, this technique uses a solid column or beads to adsorb the nucleic acids. Solid phase isolation is more expensive, requires columns or beads and requires cell lysis.

Answer: Presence of RNAse

RNA, ribonucleic acid, is particularly libale, or unstable, because of the presence of RNAses, which is an enzyme readily found in nuclei that degrade RNA. These enzymes must be eliminated or inactivated before RNA isolation.

Answer: rRNA, tRNA, mRNA

Many types of RNA, ribonucleic acid, are present in most cells. The most abundant RNA in cells is ribosomal RNA (rRNA). 80-90% of all RNA is rRNA. Transfer RNA (tRNA) accounts for 10-15%, and messanger RNA (mRNA) makes up 2-5% of the total RNA.

Answer: Uppermost phase

Organic extraction technique uses an aqueous, liquid, combination of phenol and cholorform to isolate the nucleic acid. The nucleic acid will dissolve in the uppermost, hydrophilic (water-loving) phase. The hydrophobic (water-hating) or lowermost phase contains lipids, and the other components such as cell debris will collect in the interface between the other two layers.

Answer: Between 1.6 and 2.0

When evaluation the purity of an extracted nucleic acid sample, optical density, or the solution's ability to block light, can be useful. Optical density is commonly read at 260 nanometers (nm) and 280 nanometers (nm). If the 260nm/280nm ratio is less than 1.6, this is indicative of protein contamination. If the ratio is greater than 2.0, there is strong evidence of RNA contamination in the sample.

Answer: Ethidium bromide

Ethidium bromide is a nucleic acid-specific dye used on the agarose gel, the media used in electrophoresis. The other three dyes are all fluorescent dyes used in fluorescent spectroscopy.

Answer: With low agarose concentrations

The spaces or pores in the gel, the media used in electrophoresis, are determined by the concentration of the agarose, which is a compound made from algae. The more concentrated the agarose, the more restricting the gel becomes. Therefore, smaller peices of DNA are resolved on more concentrated agarose gels and larger peices are best resolved in lower agarose concentrations.

Answer: Carry the current and protect the samples

The buffer system uses its electrochemical characteristics to carry the current and protect the samples. The buffer is a weak acid and its conjugate base, allowing the pH of the buffered solution to remain constant. This maintenance of the pH through the exchange of protons, or hydrogen ions, is responsible for the current and sample protection.