Question

1- Which are the differences between the PCR we used in the lab and DNA replication in human cells?

	A.	PCR replicates specific DNA segments while in human cells all the DNA is replicated
	B.	PCR uses high temperature to dissociate the DNA strands while DNA replication in human cells uses helicase
	C.	PCR uses a high temperature resistant polymerase while the DNA polymerase from human cells would denature at high temperatures
	D.	A and B are true
	E.	A, B and C are tru

Answer 1

• Polymerase chain reaction, or PCR, is a technique to make many copies of a specific DNA region in vitro (in a test tube rather than an organism). And in humans during that process of cell division, all of the information in a cell has to be copied, and it has to be copied perfectly. And so DNA is a molecule that can be replicated to make almost perfect copies of itself.

• The initial step in the PCR process is a high-temperature denaturation step. The temperatures used in this step (typically 92–98 °C) cause breakage of the hydrogen bonds that hold the DNA double helix together. This results in separation of the double-stranded DNA into single-stranded DNA.

• DNA replication proteins also known as helix destabilizing enzyme. Helicase separates the two strands of DNA at the Replication Fork behind the topoisomerase. The enzyme responsible for catalyzing the addition of nucleotide substrates to DNA in the 5′ to 3′ direction during DNA replication.

• PCR relies on a thermostable DNA polymerase, Taq polymerase, and requires DNA primers designed specifically for the DNA region of interest.

• In PCR, the reaction is repeatedly cycled through a series of temperature changes, which allow many copies of the target region to be produced.

• Its DNA polymerase is very heat-stable and is most active around 70 ° C, high temperature is used repeatedly in PCR to denature the template DNA, or separate its strands.

• Therefore option E, i.e. A,B and C are true.