MCQ MAHE 2000 Biochemistry Answer 5

The Correct Answer is A

Although life requires DNA replication, DNA replication does not require life. Thus, PCR technology can be born. PCR (long name: Polymerase Chain Reaction) is a method of producing large quantities of DNA not in a cell…but, in a laboratory. All that is required is a single segment of DNA, the replication machinery (the polymerase), primers, and a large quantity of nucleotides.

The polymerase chain reaction (PCR) is a fast and inexpensive technique used to "amplify", meaning copy, small segments of DNA. Studies of isolated pieces of DNA are nearly impossible without PCR amplification. “Often heralded as one of the most important scientific advances in molecular biology, PCR revolutionized the study of DNA to such an extent that its creator, Kary B. Mullis, was awarded the Nobel Prize for Chemistry in 1993.”

To amplify a segment of DNA using PCR, the sample is first heated so the DNA double helix structure denatures, meaning separates into two pieces of single-stranded DNA. Then, two DNA primers come in and attach to the 5’ ends of the DNA strands at a specific site on the target, template segment.

Next, an enzyme called "Taq polymerase" comes in and synthesizes, two new strands of DNA, using the original strands and the primers as templates. Taq polymerase is a polymerase that can synthesize DNA in very high temperatures. This process produces the duplication of the original target DNA. The new DNA molecule contains one old and one new strand of DNA. Then each of these strands are used to create two new exact copies of the target DNA segment, and so on, and so on.

The cycle of denaturing and synthesizing new DNA is repeated as many as 20 or 30 times. The number of DNA molecules goes up exponentially with each cycle, leading to millions of exact copies of the original target DNA segment.

The entire cycling process of PCR is automated. It is directed by a machine called a thermocycler, which is programmed to alter the temperature of the reaction every few minutes to allow DNA denaturing and synthesis to occur.

Category: MAHE 2000 MCQs