Language
Country/Area
No result found
Nature's self-healing: How does DNA replicate perfectly when cells divide?
In the field of biology, DNA replication is a crucial biological process that generates two identical DNA copies from an original DNA molecule. This process occurs in all living organisms and is the most basic link in biological inheritance. Whether growing or repairing damaged tissue, DNA replication is essential because it ensures that each new cell gets its own copy of DNA.
Cells are unique in that they can divide, making DNA replication crucial.
The structure of DNA is a double helix, consisting of two complementary strands. During replication, these strands are separated, and each strand of the original DNA molecule serves as a template for producing its corresponding strand, a process called semiconservative replication. In this way, the newly generated double helix will consist of one original DNA strand and one newly synthesized strand. The proofreading and error checking mechanisms in this process allow DNA to be copied with almost perfect accuracy.
The structure of DNA
DNA exists in a double-stranded structure, with the two strands curled together to form a characteristic double helix shape. Each single strand of DNA is composed of four nucleotides. These nucleotides are composed of deoxyribose sugar, phosphate, and nucleotide bases. The four types of nucleotides correspond to the four nucleotide bases, namely adenine, cytosine, guanine and thymine, referred to as A, C, G and T. Adenine and guanine are purines, while cytosine and thymine are pyrimidines.
These nucleotides are linked by phosphodiester bonds to form the phosphate-deoxyribose backbone of the DNA double helix, with their bases pointing inwards, that is, toward opposite strands. Nucleotide bases form complementary pairs through hydrogen bonds, with two hydrogen bonds between adenine and thymine, and three hydrogen bonds between guanine and cytosine.
This makes the structure of DNA not only stable, but also provides a precise mechanism for transmitting genetic information.
DNA polymerase and its functions
DNA polymerases are a family of enzymes that perform all forms of DNA replication. These polymerases cannot start new strands on their own, but they can extend an existing strand of DNA or RNA. During the synthesis process, RNA primers must first be created and paired with the template DNA strand, and then DNA polymerase extends this strand by joining new nucleotides, forming phosphodiester bonds one by one.
The process of DNA polymerization requires the hydrolysis of high-energy phosphate bonds as energy to drive. Generally speaking, DNA polymerase can perform proofreading while continuing to extend the chain, helping to correct incorrect base pairing and thereby improve the accuracy of replication.
DNA replication process
The DNA replication process can be divided into three main steps: initiation, elongation and termination. First, DNA must be replicated before cells can divide, and in this process, the initiation phase is crucial. At the initiation of replication, a group of large protein complexes are formed at specific sites on DNA, called the prereplication complex.
As the cell cycle changes, these promoter proteins assemble to form complexes that open the DNA double helix. Thus, the separation of the DNA double strands allows DNAB polymerase to replicate more easily.
This process ensures that the newly synthesized DNA can be accurately paired along the template, maintaining the stability of the genetic information.
When DNA polymerase tries to read the template nucleotide, it needs to synthesize a new DNA strand in the correct direction, which is why the activity of DNA polymerase is unidirectional, that is, it can only go from the 3' end to New nucleotides are added to the 5' end. This introduces the formation of a lagging strand, which is more complex to synthesize because it involves the synthesis of short fragments.
Formation of replication fork
In the process of DNA replication, the replication fork is a special structure formed by a helicase that works in the DNA double helix. These helicases break the hydrogen bonds holding the DNA strand together, eventually forming two branches containing single strands of DNA. These two strands serve as templates that will form new leading and lagging strands, thereby promoting DNA replication.
As DNA polymerase begins to synthesize new strands at the replication fork, the further separation of the DNA causes the DNA double helix to push outward and enter the next stage of elongation.
Throughout the process, the formation and operation of replication forks gives the opportunity to relax and extend new DNA. This replication system is a perfect example of how nature maintains its self-repair.
Although science has long revealed the detailed process of DNA replication, it still makes us think about how this natural self-repair mechanism was formed in the long process of evolution?
