In preparation for mitosis, DNA is copied; this is called DNA __.
The correct answer and explanation is:
The correct answer is replication.
DNA replication is the process by which a cell copies its DNA in preparation for cell division, which is a crucial step before mitosis. The purpose of DNA replication is to ensure that each daughter cell receives an identical copy of the genetic material during cell division.
DNA replication occurs during the S phase of the cell cycle, which is the phase preceding mitosis. The process begins at specific locations on the DNA called “origins of replication,” where the DNA double helix is unwound by enzymes. This unwinding exposes the two strands of DNA, which act as templates for the synthesis of new complementary strands.
The key players in DNA replication are enzymes such as helicase, which unwinds the DNA, and DNA polymerase, which adds new nucleotides to form the complementary strand. The enzyme ligase is responsible for sealing any gaps in the DNA backbone after the new strand is synthesized. The end result is two identical DNA molecules, each consisting of one old strand and one newly synthesized strand. This mechanism is known as semiconservative replication, as each new DNA molecule conserves one of the original strands.
DNA replication is a highly regulated and accurate process, but errors can still occur, leading to mutations. To minimize these errors, the cell has repair mechanisms in place, such as proofreading by DNA polymerase and post-replicative mismatch repair.
Once DNA replication is complete, the cell proceeds to the G2 phase, where it prepares for mitosis. At this point, the chromosomes condense and become visible under a microscope, and the cell ensures that all the necessary components are ready for the successful division into two daughter cells.