Question

Okazaki is known for his contribution to the understanding of:
A. Transcription
B. Translation
C. DNA replication
D. Mutation

Answer 1

Reiji Okazaki, along with his wife and other colleagues is known for discovering the role of Okazaki fragments in the process of duplication of the double-stranded genetic material.

Complete answer: Okazaki fragments: Okazaki fragments are short sequences of DNA nucleotides which are synthesized discontinuously in fragments and joined later on by enzyme ligase to create the lagging strand during DNA replication. Following are the steps included in DNA replication:
a) Formation of replication fork: the DNA is unwinded into two single strands (enzymes involved: DNA helicase)The replication fork is bidirectional. The strand oriented in 3’ to 5’ direction is leading strand and strand in 5’ to 3’ direction is lagging strand.
b) Binding of primer: A short fragment of RNA primer binds to 3’ end of the unwinded DNA strand. It is catalysed by the enzyme DNA primase.
c) Elongation: In this process, DNA polymerase III is the main replication enzyme. The leading strand is synthesized continuously in 5’ to 3’ direction. However, replication on the lagging strand is done by Okazaki fragments in a discontinuous manner.
d) Termination: It involves the removal of RNA primers and their replacement with appropriate bases and proofreading of newly formed DNA strands by DNA ligase.
Hence, the correct answer is option C.

Note: Reiji Okazaki and Tsuneko Okazaki are known Japanese molecular biologists, known for their work on DNA replication. Reiji Okazaki died of leukaemia at the age of 44 because of heavy irradiation during the first atomic bombing of Hiroshima.