What is DNA Replication?
DNA replication is the process by which cells create a copy of their genome. It is essential to cell growth because new cells must contain the same genetic information as the original. The replication process produces two separate DNA molecules: one new strand and one old strand. DNA replication is a semi-conservative process. As a result, each copy of DNA is half the original strand, half the new strand, and the final product is a double helix.
In the Hershey Chase experiment, DNA was labeled with a unique number. It is composed of 40% guanine and 40% thymine, which are complementary bases. During DNA replication, an enzyme called D. N. A. Helix unwinds each stand, adding complementary bases to the new strand. This process continues for a while, until the original strand is regenerated.
The process of DNA replication occurs in the S phase of the cell cycle, just before cell division. The objective of DNA replication is to produce new DNA strands, not new cells. The leading strand of DNA is synthesized first and is called the leading strand. The lagging strand is formed away from the replication fork.
The end of a chromosome is also protected, as DNA polymerase is unable to extend the end of a chromosome without a primer. In addition, the end of the chromosome is shortened. This happens because the telomere is a repetitive sequence that is located close to the ends of the chromosome. Eventually, these end segments break and prevent further cell division.
During DNA replication, several “bubbles” form. The leading strand of a bubble replicates a part of the other strand. The second strand replicates the lagging strand of the chromosome. During this process, the DNA polymerase adds nucleotides to each separate strand. After this, the backbone is sealed with a DNA ligase.
This process is complex and involves multiple enzymes. The first enzyme, primase, binds to the template strand and produces an RNA primer. DNA polymerase then walks along the template strand and adds a nucleotide to the preceding nucleotide. This process is known as a replication cycle.
DNA replication is extremely accurate. It makes only one mistake in every 109 nucleotides copied. This number is much higher than expected based on complementary base-pairing accuracy. There are also some cases when a mistake is made in DNA replication, which are known as mismatches. These mistakes can be corrected using the mismatch repair mechanism. Moreover, errors in DNA replication are much more easily corrected at the 3′ end than at the 5′ end.
The error rate in RNA synthesis and translation is one in 104. Compared to DNA replication, RNA synthesis and translation errors are 100,000 times more frequent. DNA replication has numerous proofreading processes that help prevent errors.