MCAT Question of the Day
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    Q:

    		 SDS is a negatively charged detergent used to disrupt noncovalent bonds between amino acids in a protein. One molecule of SDS binds on average to two residues of a protein. The protein segments are then separated by gel electrophoresis (an electric field is applied to the gel containing the protein segments) on the basis of molecular weight. The rate of movement of the protein through the gel is inversely proportional to the log of the molecular weight.

    The separation of nucleic acids by electrophoresis does not require SDS. Why?

    		 

    A

    		 There are no residue groups on nucleic acids to which SDS can bind

    B

    		 Nucleic acids can separate based on their hydrophobicity without the binding of SDS

    C

    		 Nucleic acids have phosphate groups that contribute net negative charges proportional to their size

    D

    		 Nucleic acids do not have tertiary structures like protein that need to be disrupted



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