SDS-PAGE gels are made of acrylamide and bis-acrylamide since these two create a small sieving. Mark theINCORRECT statement

Question

SDS-PAGE gels are made of acrylamide and bis-acrylamide since these two create a small sieving. Mark theINCORRECT statement

BlackTom AI · Accepted Answer

Re-stating the question and options to set the stage:
Question: SDS-PAGE gels are made of acrylamide and bis-acrylamide since these two create a small sieving. Mark the INCORRECT statement
Answer options:
1) The sieving in these gels can separate large molecules of DNA
2) SDS-PAGE separates proteins based on size/mass because SDS provides a common charge to all proteins
3) depending on the concentration of acrylamide and bis-acrylamide either larger or smaller proteins can be defined
4) The sieving in these gels can separate large molecules of DNA
5) SDS denatures all non-covalent interactions

Option 1: The sieving in these gels can separate large molecules of DNA
This statement is misleading because SDS-PAGE is designed to separate proteins, not DNA. The gel matrix does create a size-based sieve, but DNA separation is typically performed with agarose gels rather than acrylamide gels used in SDS-PAGE. Therefore this option misstates the primary purpose of SDS-PAGE and is considered incorrect.

Option 2: SDS-PAGE separates proteins based on size/mass because SDS provides a common charge to all proteins
This is a correct and core description of SDS-PAGE. Detergent SDS denatures proteins and coats them with a uniform negative charge proportional to length, so migration in the gel depends largely on size, not on intrinsic shape or charge differences. This statement accurately reflects the fundamental principle of SDS-PAGE.

Option 3: depending on the concentration of acrylamide and bis-acrylamide either larger or smaller proteins can be defined
This statement captures the concept of gel pore size: increasing crosslinker (and overall acrylamide concentration) tightens the gel, restricting movement and resolving smaller proteins, while lower concentrations yield larger pores. Depending on composition, the apparent separation range shifts to favor different size ranges. This is a true and nuanced description of gel behavior.

Option 4: The sieving in these gels can separate large molecules of DNA
This option echoes the same idea as Option 1 but is phrased to emphasize DNA separation. As above, SDS-PAGE is not used for separating DNA; DNA is typically separated by agarose electrophoresis. Thus, this statement is incorrect for the same fundamental reason: it attributes DNA separation to SDS-PAGE, which is not accurate.

Option 5: SDS denatures all non-covalent interactions
SDS disrupts many non-covalent interactions within proteins by binding along polypeptide chains and imparting a uniform charge, leading to denaturation of secondary and tertiary structures. While it is broadly true that SDS disrupts non-covalent interactions, the qualifier “all” is an absolute claim that can be too strong in some contexts (e.g., some strong protein-protein interactions or persistence of some structural motifs under certain conditions). In general, for practical SDS-PAGE purposes, SDS effectively denatures proteins by disrupting most non-covalent interactions, so this statement is largely acceptable but one could argue about absolutes. Given standard teaching, it is treated as a correct description of SDS’s effect.

In summary, the statements that claim SDS-PAGE can separate DNA (Options 1 and 4) are incorrect because the technique targets proteins, not DNA. The statements about protein separation by size with a uniform charge from SDS (Option 2) and about tunability of separation via acrylamide/bis-acrylamide concentration (Option 3) are correct. The statement about SDS denaturing non-covalent interactions (Option 5) is broadly consistent with SDS’s mechanism, though the use of absolute language (“all”) can be Points of nuance in advanced discussions, but is generally viewed as correct in standard contexts.

SDS-PAGE gels are made of acrylamide and bis-acrylamide since these two create a small sieving. Mark theINCORRECT statement Single choice

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