Replication

Replication is a process that occurs in all living organisms as the basis for biological inheritance. This is the process by which an organism's DNA is copied during the cell cycle. The copied material, which has the same genetic makeup as the original, is referred to as a replica.

Overview

Replication involves the separation of the DNA molecule into two strands, followed by the synthesis of new strands to match each of the separated strands. The resulting double helixes are identical to each other and to the original. This process is essential for cell growth, repair, and reproduction in organisms.

Process

The process of replication begins with the unwinding of the double helix to expose the bases in each strand of DNA. The location where this occurs is called the origin of replication. The unwinding is done by an enzyme called helicase, which breaks the hydrogen bonds holding the two DNA strands together.

Once the DNA is unwound, another enzyme called DNA polymerase adds new bases to the strand. This is done in a 5' to 3' direction, meaning that new nucleotides are added at the 3' end of the new strand.

Replication Fork

The replication fork is a structure that forms within the nucleus of a dividing cell. It is created by helicases, which break the hydrogen bonds holding the two DNA strands together. The resulting structure has two branching "prongs", each one made up of a single strand of DNA.

Leading and Lagging Strands

During replication, one strand of DNA, known as the leading strand, is replicated continuously in the 5' to 3' direction. The other strand, known as the lagging strand, is replicated discontinuously in short sections known as Okazaki fragments.

Termination

Replication ends when the new DNA molecules fully separate from the original DNA. In eukaryotes, each linear end of DNA molecule contains telomere sequences which are replicated with the help of an enzyme called telomerase.

See Also

• DNA
• Cell cycle
• DNA polymerase
• Helicase
• Okazaki fragments
• Telomerase

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