Profile
Settings
Refer your friends
Sign out
Introduction
Copying of DNA is a process in which a molecule of DNA makes two identical copies of itself inside a reproductive cell. The process through which DNA creates multiple copies of itself is known as replication. Initiation, elongation, and termination are three steps of biological polymerization.The complete cycle is carried out with the help of enzymes, the most important of which being DNA-dependent polymerase.
When does dna copying occur
During cell division, DNA replication or copying takes place. DNA replication occurs during the cell cycle’s ‘S’ phase (synthesis phase). The chromosomes segregate during the ‘M’ phase, also known as mitosis.
The DNA content of chromosomes is duplicated during the ‘S’ phase, which is an essential step in ensuring that daughter cells have the same quantity of DNA as the parent cell. Growth differentiation and gamete production require cell division. G1, S, and G2 are the three stages of interphase. DNA copying occurs in the interphase nucleus’ S phase.
DNA REPLICATION
DNA replication is a term that refers to the replicating of DNA. It is required for the genome’s continuity during cell proliferation, repair, and gamete production.
Semiconservative DNA replication means that one of the parent strands is conserved while the other strand of double-stranded DNA is generated from scratch. DNA replication in eukaryotes is sporadic. The reaction is catalysed in the 5’3′ direction by DNA polymerase.
Replication begins at the replication origin, with the unwinding of DNA double strands generating a replication fork. The unwinding is catalysed by the enzyme DNA helicase. The leading strand is duplicated continually while the lagging strand is reproduced infrequently, resulting in Okazaki fragments that are linked by DNA Ligase.
It’s worth noting that the cell’s chromosome number stays the same during the ‘S’ phase, with just the DNA content doubling. The nucleus is where DNA duplication takes place. During the ‘S’ phase, centriole duplicates in the cytoplasm as well.
How is DNA Replicated
The three major processes of replication are the opening of the double helix and separation of the DNA strands, priming of the template strand, and creation of the new DNA segment. During separation, the two strands of the double helix of DNA uncoil at a specific point known as the origin.
After that, a combination of enzymes and proteins prepare the strands for duplication. Finally, the assembly of the new DNA strands is organised by a specific enzyme called DNA polymerase. The three-stage process outlined below is applicable to all cells; however, depending on the organism and cell type, specific variations within the process may occur.
What triggers replication
Starting DNA replication requires two stages. An initiator protein unwinds a small stretch of the double helix of DNA first.The helicase protein subsequently binds to the hydrogen bonds between the bases on the DNA strands and shatters them, separating the two strands . As it moves along the DNA molecule, the helicase continues to break hydrogen bonds, separating the two polynucleotide chains.
Meanwhile, when the helicase divides the strands, another enzyme known as primase attaches itself to each strand for a brief period of time and lays the groundwork for replication. A primer is a short stretch of nucleotides that serves as the foundation.
How are DNA strands replicated
After the primer is in place, DNA polymerase wraps itself around a single, unwinding polynucleotide strand, adding new nucleotides to the exposed nitrogenous bases. In this way, the polymerase builds a new DNA strand on top of the existing one.
The new strand is built from the pool of free-floating nucleotides that surround the present strand as DNA polymerase proceeds down the unwound DNA strand . The nucleotides in the new strand are coupled with partner nucleotides in the template strand; A and T nucleotides always pair with one another due to their chemical shapes, the nucleotides C and G are always paired together.Complementary base pairing is the term for this phenomena.
As a result, two complementary strands of DNA are produced.
Base pairing guarantees that the nucleotide sequence in the current template strand is exactly matched to a complementary sequence in the new strand, ensuring that the template strand’s anti-sequence is maintained. When the new strand is reproduced later, the complementary strand will have the same sequence as the original template strand. Replication proceeds as a series of sequence and anti-sequence copies as a result of complementary base pairing, retaining the original DNA’s code.
How long does replication take
- coli is a prokaryotic bacterium. Replication can happen at 1,000 nucleotides per second in E. coli. In eukaryotes, human DNA replicates at 50 nucleotides per second. Multiple polymerases can synthesise two new strands at the same time using each unwinding strand from the original DNA double helix as a template in both circumstances, allowing replication to happen so swiftly. The leading strand is one of these initial strands, while the trailing strand is the other. As demonstrated in Figure 5, the leading strand is continually produced. The lagging strand, on the other hand, is made up of small, independent fragments that are eventually brought together to form a whole, newly copied strand.
Importance Of Dna Copying In Reproduction
An individual’s body design is determined by their DNA. The DNA that is passed down from parents to kids gives them a similar appearance. Reproduction necessitates DNA replication. During replication, more copies of DNA are created, which are required for the formation of new cells after cell division. Furthermore, tiny deviations in the long run are caused by minor changes in DNA replication.
DNA Copying
DNA copying refers to the process of replicating DNA during cell division.
It’s crucial to pass on the genes of the parent(s) to the next generation of the same species. This factor determines whether or not a species will continue to exist. This technique is particularly crucial in asexually reproducing organisms. Only one parent is involved in such organisms, and there is no other source of variation in the DNA of the progeny of the parent.
Example. For instance, if a species can live in sufficient water at a certain temperature. However, climate changes may cause a shift in water temperature, causing the species to die and become extinct. However, this does not occur in nature because there is always some variation in DNA replication and some species that are nearly identical. Some individuals of this species of bacteria will be able to survive in warmer water due to this minor mutation in their DNA, ensuring the species’ survival. Variations included in DNA during replication play a significant role in this process.
Conclusion
Life would not exist without DNA. It has a high rate of reproduction, which implies that the parents’ qualities will be passed on to the following generation. It is changeable, which means it allows for variation, which is necessary for evolution to take place. It also produces proteins that aid in the expression of the organism’s genes and characteristics.
