Question

All the molecules generated during PCR will not be full length. Some will also be of intermediate length. Which of the statements is correct?

(a) After first cycle, majority of the molecules will be full length and only some will be of intermediate length

(b) In the next cycle, each intermediate molecule will generate one intermediate molecule and one target molecule

(c) The number of full length molecules increase as number of cycles proceed

(d) The number of intermediate molecules increase geometrically and the number of target molecules increase arithmetically

The question was posed to me during an online exam.

Query is from The Basic Technique in chapter Polymerase Chain Reaction of Genetic Engineering

Answer 1

Correct option is (b) In the next cycle, each intermediate molecule will generate one intermediate molecule and one target molecule

The explanation: Intermediate molecules are those which would be having primer at one end and the other end won’t be defined. After the first cycle, half of the molecules would be full length and half would be of intermediate length. In the next cycle, each intermediate molecule generates one intermediate molecule and one target molecule. Target molecule is that which is defined by primers at both the ends. The number of full length molecules remains constant. But, target molecules increase geometrically and the intermediate molecules increase arithmetically.