Copying DNA
Before cell division, DNA is replicated so that the genetic information can be passed on to the daughter cells.
Replication is semi-conservative because each DNA molecule produced contains:
- one strand retained from the parental DNA
- one strand made during replication
In this way, copies of the genetic information are maintained from one generation of cells to the next. DNA replication occurs during the S phase of interphase and supports the production of cells needed for growth and replacement.
- The DNA double helix unwinds and its two strands separate.
- Each parental strand provides a template for another strand.
- Free DNA nucleotides pair with the exposed bases according to complementary base pairing.
- DNA polymerase links neighbouring nucleotides as the new strands form.
- Hydrogen bonds form between complementary bases of the parental and newly synthesised strands.
- The result is two DNA molecules, each composed of one parental strand and one newly formed strand.
Exam Tip: Define semi-conservative precisely: each resulting DNA molecule has one parental strand and one newly synthesised strand.