Below are a few statements about enzymes and their molecular reaction functions.

 1. Below are a few statements about enzymes and their molecular reaction functions.

A.   Alkaline phosphatases remove 3' phosphates from DNA and RNA.

B. S1 nuclease removes single-stranded regions from partially double-stranded DNA.

C.  5' end-labeling of DNA molecules can be done by using polynucleotide kinase, which transfers a 32P-labelled phosphate group to the 5' end of dephosphorylated DNA.

D. 3'-5' exonuclease activity of Taq polymerase releases the reporter from the 3' end of Taqman probes in qPCR.

Which one of the following options represents a combination of all correct statements?

1. A and B

2. B and C

3. B and D

4. A and C

Answer: 2. B and C

Explanation:

           Enzyme(s)                                                                                 Function

 Type II restriction endonucleases                                Cleave DNA molecules at specific base sequences

  Alkaline phosphatase                                                  Removes terminal phosphates from the 5′ or 3′                                                                                                                         end (or both)

Polynucleotide kinase                                                    Adds a phosphate to the 5′-OH end of a                                                                                                           polynucleotide to  label it or permit ligation

Exonuclease III                                                              Removes nucleotide residues from the 3′ ends of                                                                                                  a DNA strand 

Terminal transferase                                                     Adds homopolymer tails to the 3′-OH ends of a                                                                                                         linear duplex  

  Bacteriophage λ exonuclease                                      Removes nucleotides from the 5′ ends of a                                                                                                     duplex to expose single-stranded 3′ ends .

S1 nuclease                                                                  Breaks down single-stranded DNA and RNA.