3.

Separation methods

Multiple Completion
(A question or incomplete statement is followed by four numbered completions, one or more of which are correct.
Select: A: if 1, 2 and 3 are correct;
B: if 1 and 3 are correct;
C: if 2 and 4 are correct;
D: if only 4 is correct;
E: if all four are correct.)

1.___ Which of the following methods is suitable for the charge-based separation of
proteins?
1. SDS-polyacrylamide gel electrophoresis
2. isoelectric focusing
3. gel filtration
4. ion-exchange chromatography

2.___ Which method is suitable for the separation of two proteins having the same size and
isoelectric point?
1. Affinity chromatography
2. Two-dimensional gel electrophoresis
3. Immunoprecipitation
4. Ion-exchange chromatography

Five-choice Completion

(This type of question consists of a question or incomplete statement followed by five suggested answers or
completions. Select the one best answer.)

3.___ Proteins A and B are being separated by gel filtration. Protein A is eluted in
fraction 10, while protein B in fraction 13. What is your interpretation of this
observation?
A. Protein A is larger than protein B.
B. Protein A is smaller than protein B.
C. Protein A is rich in lysine, while protein B in glutamic acid.
D. Protein A has a lower pI than protein B.
E. Protein A is more hydrophobic than protein B.
Four-choice Association
(In this type of question a set of lettered headings is followed by a list of numbered words or phrases.
Select: A: if the word or phrase is associated with A only;
B: if the word or phrase is associated with B only;
C: if the word or phrase is associated with A and B;
D: if the word or phrase is associated with neither A nor B.)

A. Equilibrium density (isopycnic) gradient centrifugation

B. Rate zonal (hypopycnic) gradient centrifugation
C. Both of them
D. Neither of them

4.___ It is the method of choice to separate bromodeoxyuridine labelled and unlabelled

DNA.
5.___ It is the method of choice to separate 15N- and 14N-containing DNA molecules.
6.___ It is used to separate polysomes from the ribosomal fraction.
7.___ It It is the method of choice to separate the heavy and light chains of mitochondrial
DNA.
8.___ The density of its gradient is higher in layers closer to the top of the centrifuge tube.
9.___ CsCl is used to form its gradient.
10.___ It can be used to isolate satellite DNA.
11.___ This technique is the best choice to purify polyadenylated mRNAs.
12.___ It is used to separate basic and acidic proteins from each other.

A. Gel filtration
B. SDS polyacrylamide gel electrophoresis
C. Both of them
D. Neither of them
13.___ It can be used to separate various proteins from each other.
14.___ The smaller the molecule the faster it moves during this separation procedure.
15.___ Detergent treatment is an obligatory step of the technique.
16.___ The size of the molecule influences its separation with this technique.
17.___ CsCl gradient centrifugation separates based on the same property of the
molecules as this method.
 A. Agarose gel electrophoresis
B. SDS-polyacrylamide gel electrophoresis
C. Both of them
D. Neither of them

18.___ Separates molecules according to their size.

19.___ Separates molecules based on their charge.
20.___ Macromolecules move toward the negative pole during this type of electrophoresis.
21.___ The pore size of the gel is determined by the concentration of its material.
22.___ Coomassie blue staining can be used to visualize the samples separated by this
method.
23.___ It is used to separate DNA fragments for restriction mapping.

Five-choice Association
(This type of question consists of a list of lettered headings followed by a list of numbered words or phrases. For
each numbered word or phrase, select the one heading which is most closely related to it.)

A. Formaldehyde-agarose gel electrophoresis

B. Polyacrylamide gel electrophoresis
C. Isoelectric focusing
D. All three of them
E. None of them
24.___ The separation is independent of the molecular weight of the molecules to be
separated.
25.___ The migration of molecules is happening in an electric field.
26.___ The migration of separated molecules stops reaching a certain pH value of the gel.
27.___ This is a step of Northern blotting.
28.___ This method is used in DNA sequencing.
Variation relationship
(This type of question consists of pairs of phrases which describe conditions or quantities which may or may not
vary in relation to each other.
Select: A: if increase in the first is accompanied by increase in the second or if decrease in the first
is accompanied by decrease in the second;
B: if increase in the first is accompanied by decrease in the second or if decrease in the
first is accompanied by increase in the second;
C: if changes in the second are independent of changes in the first.)

29.___ A: The density of an RNA molecule.

B: The rate of migration of the RNA molecule during agarose gel
electrophoresis.
30.___ A: The total number of A-T and G-C base pairs in a double stranded DNA molecule.
B: The electrophoretic mobility of the same DNA molecule.

Relationship analysis
(This type of question consists of a sentence with two main parts: an assertion and a reason for that assertion.
Select: A: if both assertion and reason are true statements and the reason is a correct
explanation of the assertion;
B: if both assertion and reason are true statements but the reason is not a correct
explanation of the assertion;
C: if the assertion is true but the reason is a false statement;
D: if the assertion is false but the reason is a true statement;
E: if both assertion and reason are false statements.)

31.___ The superspiralized form of the plasmid migrates faster in an agarose gel than the
nicked circular one, BECAUSE the superspiralized form is more compact.
Study the figure below and answer the questions.

The figure shows an experiment that combines two different methods (steps I. and II). In the
first step, microsomal fraction (from which membranes have been removed) was used. In step
two, macromolecules of one of the fractions from step I. were used. Study the figures and
answer the following questions.

Five-choice Completion
(This type of question consists of a question or incomplete statement followed by five suggested answers or
completions. Select the one best answer.)

32.___ Which of the following methods was used in step I.?

A. differential centrifugation
B. equilibrium density (isopyknic) gradient centrifugation
C. rate zonal (hypopyknic) gradient centrifugation
D. SDS-polyacrylamide gel electrophoresis
E. none of the above
33.___ Which of the following molecules are marked in the drawing as 5 and 6?

A. 5: DNA, 6: protein
B. 5: protein, 6: DNA
C. 5: rRNA, 6: mRNA
D. 5: mRNA, 6: rRNA
E. None of them

34.___ Which of the following statements is true?

A. Molecules labeled 5 can be isolated by CsCl gradient centrifugation after

step I.
B. Molecules labeled 5 can be isolated by gel filtration after step I.
C. Molecules labeled 6 can be isolated by CsCl gradient centrifugation after
step I.
D. Molecules labeled 6 can be isolated by oligo(d)T-cellulose affinity
chromatography after step I.
E. None of the above

Multiple Completion

(A question or incomplete statement is followed by four numbered completions, one or more of which are correct.
Select: A: if 1, 2 and 3 are correct;
B: if 1 and 3 are correct;
C: if 2 and 4 are correct;
D: if only 4 is correct;
E: if all four are correct.)

35.___ Which separation method is indicated by arrow 8?

1. SDS-polyacrylamide gel electrophoresis
2. agarose gel electrophoresis under alkaline conditions
3. non-denaturing polyacrylamide gel electrophoresis
4. formaldehyde-agarose gel electrophoresis
Relationship analysis
(This type of question consists of a sentence with two main parts: an assertion and a reason for that assertion.
Select: A: if both assertion and reason are true statements and the reason is a correct
explanation of the assertion;
B: if both assertion and reason are true statements but the reason is not a correct
explanation of the assertion;
C: if the assertion is true but the reason is a false statement;
D: if the assertion is false but the reason is a true statement;
E: if both assertion and reason are false statements.)

36.___ The electrode labeled 9 must be positively charged, BECAUSE macromolecules 5 and
6 loose their original charge during process 7 and become negatively charged.

Study the figure below and answer the questions.

A280 NH4Cl (M)

B 0.8

0.6

0.4
A
0.2

5 10 15 20 25 30 35
Fraction number

Quantitative Comparison
(In this type of question paired statements describe two entities that are to be compared in a quantitative sense.
Select: A: if A is greater than B;
B: if B is greater than A;
C: if the two are equal or very nearly equal.)

37.___ A. The charge of substance A at 0.2 M NH4Cl concentration.

B. The charge of substance B at 0.2 M NH4Cl concentration.

38.___ A. The charge of substance A at 0.2 M NH4Cl concentration.

B. The charge of substance B at 0.4 M NH4Cl concentration.

39.___ A. The protein content of substance A.

B. The protein content of substance B.
Five-choice Completion
(This type of question consists of a question or incomplete statement followed by five suggested answers or
completions. Select the one best answer.)

40.___ Which of the following separation methods was used in this experiment?
A. equilibrium density (isopicnic) gradient centrifugation
B. rate zonal (hypopicnic) density gradient centrifugation
C. affinity chromatography
D. ion-exchange chromatography
E. none of the above

Study the figure below and answer the questions.

Five-choice Completion
(This type of question consists of a question or incomplete statement followed by five suggested answers or
completions. Select the one best answer.)

41.___ Which of the following separation methods was used in this experiment?
A. ion exchange chromatography
B. rate zonal (hypopycnic /sucrose) density gradient centrifugation
C. equilibrium density (isopycnic / cesium chloride) density gradient
centrifugation
D. gel filtration
E. none of the above methods
Figure Analysis
(The following statements are related to the information presented above. Based on the information given.
Select: A: if the statement is supported by the information given;
B: if the statement is contradicted by the information given;
C: if the statement is neither supported nor contradicted by the information given.)

42.___ Molecules in fraction 15 have the largest size.

43.___ All 3 fractions (5,10,15) contain chromatin.
44.___ Molecules in fraction 15 have the strongest charge.
45.___ Electrophoresis of these molecules in a non-denaturating polyacrylamide gel would
also result in 3 fractions.
46.___ Molecules in fraction 5 have the lowest density.
Correct answers:

1. C 11. D 21. C 31. A 41. C

2. B 12. D 22. B 32. C 42. C
3. A 13. C 23. A 33. C 43. B
4. A 14. B 24. C 34. D 44. C
5. A 15. B 25. D 35. D 45. C
6. B 16. C 26. C 36. C 46. B
7. A 17. D 27. A 37. B
8. D 18. C 28. B 38. C
9. A 19. D 29. C 39. B
10. A 20. D 30. B 40. D

Supported by a grant from the European Union (TÁMOP-4.1.1.C-13/1/KONV-2014-

0001).