You have large 4 DNA duplexes 4 pieces that are 1 Big strand

You have large 4 DNA duplexes (4 pieces that are 1 Big strand duplexed with a complementary Big strand). Assume you have infinite amount of 2 primers that will amplify a small region of DNA using PCR.

What is the minimum number of cycles of PCR must you perform so you have >100 pieces of the Short-Short duplex that is amplified.

Solution

Polymerase chain reaction is based on the way DNA replication. During DNA replication, the two strands of each DNA molecule separate, and DNA polymerase enzyme, brings the nucleotides to form two new complementary strands for each of the original strands. The original strands serve as templates for the new strands leading and lagging strand. The new strands are assembled such that each nucleotide in the new strand is determined by the corresponding nucleotide in the template strand. The nucleotides adenine (A) and thymine (T) always lie opposite each other, as do cytosine (C) and guanine (G). Because of this base-pairing specificity, each newly synthesized partner strand has the same sequence as the original partner strand, and replication produces two identical copies of the original double-stranded DNA molecule.

In PCR, a DNA sequence amplifies the \"target\" sequence, undergoes about thirty-thirty five rounds of replication. During each replication cycle, the number of molecules of the target sequence doubles, because the products and templates of one round of replication all become the templates for the next round. After n rounds of replication, 2n copies of the target sequence are theoretically produced, logarathimcally. After thirty cycles, PCR can produce 230 or more than ten billion copies of a single target DNA sequence. This is called a polymerase chain reaction because DNA polymerase catalyzes a chain reaction of replication.

Since it is a logarithmic reaction, 2^x=100.

Thus x=6.64. So a minimum of 7 cycles of PCR is required to get >100 pieces of desired size amplified DNA