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B. dsDNA replication
C. Single stranded DNA replication
D. Translation
Okazaki fragments are formed in
A. TranscriptionB. dsDNA replication
C. Single stranded DNA replication
D. Translation
Ans. B. (dsDNA replication)
Explanation
• Okazaki fragments are short fragments of newly synthesized DNA strands produced during double—stranded DNA replication.
• All the known DNA polyrnerases can only synthesis DNA in one direction, the 5’ to 3’ direction.
• Okazaki fragments are short fragments of newly synthesized DNA strands produced during double—stranded DNA replication.
• All the known DNA polyrnerases can only synthesis DNA in one direction, the 5’ to 3’ direction.
•
However as the strands separate, replication forks will be moving along one
parental strand in the 3’ to 5’ direction
and 5’ to 3’ on the other
parental strand.
• On
the former, the leading strand DNA can be synthesized continuously in the 5’ to 3’ direction.
• On
the later, the lagging strand DNA synthesis can only occur when a stretch of
single stranded DNA has been exposed and proceeds in the direction opposite to
the movement of the replication fork (still 5’ to 3). It is thus discontinuous
and the series of fragments are then covalently linked by ligases to give a
continuous strand. Such fragments were first observed by Okazaki using pulse
labelling with radioactive thymidine.
• In
eukaryotes, Okazaki fragments are typically a few hundred nucleotides long,
whereas in prokaryotes they may contain several thousands of nucleotides.
