Cro is a bacterial gene regulatory protein that binds to DNA

Cro is a bacterial gene regulatory protein that binds to DNA to turn genes off. It is a symmetrical “head to head” dimer. Each of the two subunits of the dimer recognizes a particular short sequence of nucleotides in DNA. If the sequence of nucleotides recognized by one subunit is represented as an arrow (-->), so the the “head” of the arrow corresponds to DNA recognized by the “head” of the subunit, which of the following sequences in DNA represents the binding site for the Cro dimer?

A. --> -->

B. --><--

C. <--<--

D. <-- -->

Solution

As CRO protein is symmetrical and it defines as when the nucleotide sequence is read forward from one strand and backward from the other, complementary strand

CRO dimer shows answer B