You are studying a new strain of E. coli that can utilize the disaccharide melibiose very efficiently. You find that utilization depends on the enzyme melibiase, which is encoded by the gene Mel1. Mel1 is not expressed unless melibiose is present in the growth medium. Next you isolate a mutation, designated MelB–, which gives uninducible melibiase activity. Mapping experiments show that MelB– is linked to Mel1. Using an F' factor that carries the chromosomal region surrounding Mel1, you perform the following genetic tests:

                      

Describe the basic genetic properties of the MelB– mutation?

#Question id: 807

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following forces can stabilize a normal DNA double-helix?

#Question id: 807

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following forces can stabilize a normal DNA double-helix?

#Question id: 808

#Unit 1. Molecules and their Interaction Relevant to Biology

Which, if any, of the following statements is false?

#Question id: 809

#Unit 1. Molecules and their Interaction Relevant to Biology

A single-stranded DNA molecule contains 40 nucleotides with equal amounts of A, C, G, and T. This DNA strand can combine with a complementary DNA strand to form a double-stranded DNA molecule. Which of the following double-stranded DNA molecules would denature at a lower temperature than the 40 base-pair double-stranded molecule described above?

#Question id: 810

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following statements concerning the process of spontaneous folding of proteins is false?

#Question id: 811

#Unit 1. Molecules and their Interaction Relevant to Biology

Protein S will fold into its native conformation only when protein Q is also present in the solution.  However, protein Q can fold into its native conformation without protein S.  Protein Q, therefore, may function as a ____________ for protein S.