If you were to set up a PCR reaction (in vitro DNA synthesis) with a DNA template, primers, DNA polymerase, dATP, dGTP, dCTP, dTTP and a small amount of ddATP, what would be the result? If you were to set up a PCR reaction (in vitro DNA synthesis) with a DNA template, primers, DNA polymerase, dATP, dGTP, dCTP, dTTP and a small amount of ddATP, what would be the result? DNA synthesis would happen normally. All DNA molecules produced would be the same length as the template. DNA synthesis might be terminated after the addition of any adenine base (at random). DNA molecules of many different lengths would be produced. DNA synthesis would be terminated after the first adenine base is added. All DNA molecules produced would the same length

DNA synthesis might be terminated after the addition of any adenine base (at random). DNA molecules of many different lengths would be produced.

Explanation:

Polymerase chain reaction may be defined as the molecular process of increasing the amount of DNA upto several times. Three important steps in PCR - denaturation, annealing and extension.

As given in the question, dd ATP (dideoxy adenosine triphosphate) is added to the PCR reaction. ddATP lacks the hydroxyl group at 3' position of the sugar. This means the reaction will be terminated after this ddATP as no further nucleotide will be added. This will also leads to the genereation of the different length of DNA fragments as ddATP will randomly be inserted in the DNA molecule.

Thus, the correct answer is option (3) and (4).