What technique is used to produce millions of copies of a DNA sequence without using bacteria to amplify the DNA?

The technique that produces millions of copies of a DNA sequence without the requirement of bacteria for amplification is the Polymerase Chain Reaction (PCR). PCR is a revolutionary method that allows for the selective amplification of specific DNA sequences through a series of temperature cycles that include denaturation, annealing, and extension.

In the denaturation phase, the double-stranded DNA is heated to separate it into two single strands. During the annealing phase, short DNA primers complementary to the target sequence bind to the single-stranded DNA. Finally, during the extension phase, a DNA polymerase enzyme synthesizes new strands of DNA by adding nucleotides to the primed sequences. This process is repeated over multiple cycles, exponentially increasing the number of copies of the target DNA sequence.

This amplification is particularly useful in various applications, such as forensic analysis, medical diagnostics, and research, allowing scientists to obtain a sufficient quantity of DNA for various studies without needing to culture bacteria or use other organisms.