DNA Replication (Updated)

DNA is the ultimate director for cells, coding for your traits.

DNA replication is essential for cell division to ensure that the new daughter cells receive sufficient DNA. The process involves making more DNA, which is crucial for the growth and development of organisms.

DNA replication occurs in the nucleus of eukaryotic cells, but not in prokaryotic cells which lack a nucleus. Both cell types undergo DNA replication before division, ensuring the new daughter cell receives a copy of DNA during mitosis or meiosis in interphase.

Enzymes play a crucial role in DNA replication by speeding up reactions and breaking down molecules. Helicase unzips the two strands of DNA by breaking hydrogen bonds between bases. DNA Polymerase replicates DNA to build new strands, while Primase provides the primer for Polymerase to start working. Ligase helps glue together DNA fragments during replication.

DNA replication begins at the origin, identified by specific DNA sequences. Helicase unwinds the DNA strands while SSB Proteins prevent reannealing and topoisomerase controls supercoiling. Primase creates RNA primers for DNA polymerase to initiate replication based on complementary base pairing.

DNA strands are anti-parallel, meaning they run in opposite directions. The direction of DNA is indicated by the numbering of carbons on the sugar backbone: 5' to 3' or 3' to 5'. Each carbon on the sugar molecule is numbered clockwise after oxygen, with the 5’ carbon being outside this ring structure.

Understanding DNA Replication Process DNA replication involves the unwinding of original DNA strands, with helicase facilitating the process. Primase places primers and DNA polymerase builds new strands in a 5’ to 3’ direction. The leading strand is built continuously, while the lagging strand forms Okazaki fragments that are sealed by ligase.

Medical Implications of Understanding DNA Replication DNA polymerase proofreads during replication to prevent errors in gene coding. Detailed knowledge of DNA replication has led to medical treatments targeting harmful cell replication, such as pathogenic bacteria or cancer cells.