Replication and DNA Stages
The main function of DNA is the transmission of hereditary information. During cell division, DNA self-reproduction occurs – replication (duplication, reduplication).
Replication is the process of self-duplication of a DNA molecule, carried out under the control of enzymes.
During replication of a DNA molecule, hydrogen bonds between complementary nitrogenous bases (adenine – thymine and guanine – cytosine) are broken with the help of a special enzyme – helicase – and the chains diverge.
After the break of hydrogen bonds, with the participation of the enzyme DNA polymerase, a new (“daughter”) DNA strand is synthesized on each of the strands (for each nucleotide of the separated DNA strands, the DNA polymerase enzyme adjusts a complementary nucleotide to it). The material for synthesis is free nucleotides present in the cytoplasm of cells.
As a result of the DNA replication process, two double-stranded DNA molecules are formed, each of which includes one chain of the “parent” molecule and one “daughter” chain. These two molecules are absolutely identical, and each daughter cell, as a result of division, receives a copy of the mother’s DNA.
Stages of the DNA replication process
- First, the DNA molecule is “unlaced” – the chains of the molecule unravel and diverge (each of the two chains will serve as a kind of matrix on which a new chain will be synthesized).
- The enzyme DNA polymerase “attaches” new nucleotides to the matrix according to the principle of complementarity (to adenine – thymine, to cytosine – guanine, and vice versa).
- As soon as the process ends, new daughter (sister) molecules diverge and twist into spirals.