1.4

DNA replication is crucial for cells to divide, ensuring an equal distribution of genetic material. It is semi-conservative, meaning the original DNA strand serves as a template for new strands. The enzyme DNA polymerase is responsible for copying DNA by following complementary base pairing rules. The replication process faces challenges like unwinding coiled DNA, needing a starting point, and ensuring accuracy to prevent mutations, which can lead to diseases.

To facilitate this, proteins stabilize the DNA structure and add primers—in short RNA sequences complementary to the DNA—that provide DNA polymerase with a starting point for replication. DNA is synthesized in the 5' to 3' direction. DNA polymerase also checks for errors, removing incorrect nucleotides and replacing them with the correct ones, and joins the strands via a sugar-phosphate backbone.

In 1983, Carey Mullis developed polymerase chain reaction (PCR), allowing specific DNA sequences to be amplified millions of times outside the cell under controlled conditions. PCR, while similar to DNA replication, only targets small DNA regions and uses DNA primers, avoiding the need to remove RNA primers as in traditional replication. High heat separates DNA strands to enable copying, and repeated cycles can yield ample DNA from minimal samples, which is vital in forensic analysis.

In summary, DNA replication copies the entire genome within cells, while PCR focuses on specific gene segments through repeated cycles. Both processes depend on DNA polymerase and complementary base pairing for accuracy and efficiency in genetic replication.