1Which of the following is true of the bluewhite screening t

1.Which of the following is true of the blue/white screening technique?

Non-recombinant plasmids are white.

In recombinant plasmids, the LacZ is inactivated by the target gene.

The host strain must contain an intact lac operon.

All of the above

2. During the plasmid miniprep procedure, which of the following reagents was used to denature the nucleic acids into their single-stranded forms?

Sodium dodecyl sulfate

NaOH

Potassium Acetate

Isopropanol

3. Quantification of DNA using the Qubit system involved which of the following?

Measurement of visible light absorbance

Measurement of UV light absorbance

Measurement of fluorescence

None of the above

4. Which of the following occurs during the phenol/chloroform extraction technique?

Nucleic acids are denatured to their single-stranded versions.

Proteins are denatured.

The organic solvents each form a layer above and below the aqueous layer at the interface.

All of the above

5.What result would you expect if you omitted the ammonium acetate prior to ethanol precipitation of a DNA sample after a phenol chloroform extraction of a PCR reaction?

More Taq polymerase would be precipitated with the DNA.

Less of the DNA in the sample would be precipitated in the pellet.

More of the dNTPs would be precipitated in the pellet.

The pellet would be too difficult to resuspend in TE buffer.

Solution

1. B

In recombinant plasmids, the LacZ is inactivated by the target gene

2.B

NaOH disrupts the hydrogen bonding between the DNA bases.

3. C

Measurement of fluorescence this target-specific fluorescence, is more sensitive than UV absorbance–based quantification

4. C

The organic solvents each form a layer above and below the aqueous layer at the interface.

The proteins and hydrophobic lipids will partition into the lower organic phase while the nucleic acid remain in the upper aqueous phase.

5. C

Less of the DNA in the sample would be precipitated in the pellet. Ammonium acetate neutralize the charges on the sugar phosphate backbone making the molecule far less hydrophilic, and therefore much less soluble in water.