Compound Purification

Practice Questions

MCAT Biology › Compound Purification

Questions
5
1

To isolate DNA from a cell pellet, a student is performing an extraction using phenol and chloroform. The cells were lysed with 0.5mL of lysis buffer. 0.5mL extraction solution, consisting of phenol:chloroform:isoamyl alcohol (25:24:1), was added to the lysate. The sample was centrifuged at high speed for five minutes. The liquid in the tube was separated into three phases after centrifugation (see diagram).

Phenol_chloroform

In which layer will nucleic acids (RNA and DNA) be found?

2

To isolate DNA from a cell pellet, a student is performing an extraction using phenol and chloroform. The cells were lysed with 0.5mL of lysis buffer. 0.5mL extraction solution, consisting of phenol:chloroform:isoamyl alcohol (25:24:1), was added to the lysate. The sample was centrifuged at high speed for five minutes. The liquid in the tube was separated into three phases after centrifugation (see diagram).

Phenol_chloroform

The student saves the layer containing nucleic acids and transfers it to a new tube. The student then adds ethanol and salt, and centrifuges the solution at high speed. Where is the DNA in this new solution after centrifugation?

3

To isolate DNA from a cell pellet, a student is performing an extraction using phenol and chloroform. The cells were lysed with 0.5mL of lysis buffer. 0.5mL extraction solution, consisting of phenol:chloroform:isoamyl alcohol (25:24:1), was added to the lysate. The sample was centrifuged at high speed for five minutes. The liquid in the tube was separated into three phases after centrifugation (see diagram).

Phenol_chloroform

In which layer will lipids and other cellular debris be found?

4

To isolate DNA from a cell pellet, a student is performing an extraction using phenol and chloroform. The cells were lysed with 0.5mL of lysis buffer. 0.5mL extraction solution, consisting of phenol:chloroform:isoamyl alcohol (25:24:1), was added to the lysate. The sample was centrifuged at high speed for five minutes. The liquid in the tube was separated into three phases after centrifugation (see diagram).

Phenol_chloroform

What is the nature of each phase?

5

To isolate DNA from a cell pellet, a student is performing an extraction using phenol and chloroform. The cells were lysed with 0.5mL of lysis buffer. 0.5mL extraction solution, consisting of phenol:chloroform:isoamyl alcohol (25:24:1), was added to the lysate. The sample was centrifuged at high speed for five minutes. The liquid in the tube was separated into three phases after centrifugation (see diagram).

Phenol_chloroform

In which layer will proteins be found?

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