Okazaki fragment

Definition

noun, plural: Okazaki fragments

Relatively short fragment of DNA synthesized on the lagging strand during DNA replication.


Supplement

At the start of DNA replication, DNA unwinds and the two strands splits in two, forming two "prongs" which resemble a fork (thus, called replication fork). One of the strands goes from 5’ to 3’ and is called the leading strand; the other strand goes from a 3' to 5' and is called the lagging strand. Unlike the leading strand where DNA can be synthesized continuously the lagging strand is synthesized discontinuously in the form of short fragments called Okazaki fragments that are later connected covalently to form a continuous strand. This is because DNA synthesis can proceed only in one direction -- the 5' to 3' direction.

Okazaki fragments are originally discovered by Reiji Okazaki, Tsuneko Okazaki, and their colleagues while studying replication of bacteriophage DNA in Escherichia coli in 1968.


Word origin: named after its discoverers, Reiji Okazaki and his wife, Tsuneko Okazaki, while studying replication of bacteriophage DNA in Escherichia coli in 1968.

See also: DNA, replication, lagging strand.


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