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The unanswered questions from Dr. Randle…Okazaki Fragments


Since my group seems to always be the target of this question, and I highly doubt Dr. Randle will ever let us move on without correctly answering his questions; this week I am going to talk about Okazaki Fragments. For a quick definition, Okazaki fragments are short, newly synthesized DNA fragments that are formed on the lagging template strand during DNA replication. However, for this blog, I want to talk about the people behind this discovery.

First, let’s start by discussing a pretty cool guy named Reiji Okazaki. Mr. Okazaki was a was a pioneer Japanese molecular biologist. He was known for his research on DNA replication and for describing the role of Okazaki fragments along with his wife Tsuneko. That’s right people, credit can be given to a woman scientist who was just as smart as man scientist back in the late 60’s.

Tsuneko was pretty amazing. She won the L'Oréal-UNESCO Awards for Women in Science in 2000. She was also elected as a Person of Cultural Merit in 2015. Both Reiji and Tsuneko graduated from Nagoya University and they both became professors there. In 2015, Nagoya University created the Tsuneko and Reiji Okazaki Award, "in honor of the spirit and legacy of Professors Okazaki."

Anyways, back to the main point of this blog, Okazaki Fragments. As I am sure you know, DNA is semi-conservative and each side of the double helix run in an anti-parallel direction. As DNA is on its beginning stages of replication, it separates into two strands. These strands are known as the leading and lagging strands. Since DNA is replicated in the 5’ to 3’ direction, DNA replication can occur easily on the leading strand. However, this is not the case for the lagging strand. In 1968, Okazaki discovered the way in which the lagging strand of DNA is replicated via fragments. These small fragments known as Okazaki fragments. The term Okazaki fragment relates to short oligonucleotide sequences that are synthesized during DNA replication. These fragments are stretches of nucleotides that are synthesized in the 5’ to 3’ direction away from the replication fork.

Reiji Okazaki used E.coli in his experiments to decipher this phenomenon.  In his lab, he introduced 3T-thymidine for only ten seconds to E. coli during DNA replication. He then placed the sample in a test tube of alkaline sucrose. After doing this, he noticed that the larger DNA flowed to the bottom of the test tube and the smaller DNA did not. The larger DNA was taken out of the test tubes and were found to contain a mixture of light and heavy DNA. These results proved that half of the DNA was complete and half was in fragments. Next he decided to take the sample of E.coli and synthesized it for an additional 5 seconds. In doing so, he noticed that all the DNA was large and heavy. These findings showed that the RNA primer was removed by DNA polymerase I, and the bases were joined together by DNA ligase, leaving the newly synthesized DNA fully mature and repaired.

Okazaki fragments play an important role in DNA replication. So, after reading this blog, my 5 constant readers, who always comment, will be able to answer any question Dr. Randle asks regarding these short fragments.



Sources:


Comments

  1. JessyOctober 26, 2017 at 4:34 PM

    I never knew the full story about Okazaki fragments, and I love the history behind these kind of things. The way we discover new phenomenon and preform tests has changed so much even since this discovery in the 60's.

    ReplyDelete
  2. daniellevuOctober 27, 2017 at 8:12 AM

    We will never live this down! I've learned the basics of Okazaki fragments in cell biology and genetics, but I never knew the actual history behind them. It's nice to learn about the behind the scenes, rather than just what they are and what they can do. Nice post!

    ReplyDelete
  3. Samson NdukweOctober 27, 2017 at 12:02 PM

    Despite learning about Okazaki fragments in classes such as genetics and call biology, I was not aware of the full story behind the discovery of Okazaki fragments. P.S I loved all of the shots you fired throughout your post, extremely entertaining.

    ReplyDelete
  4. UnknownOctober 27, 2017 at 6:42 PM

    Thank you for helping me understand the basics and background of these pesky Okazaki fragments. Now if we ever play molecular jeopardy again.. we will be the real winners!

    ReplyDelete
  5. UnknownNovember 5, 2017 at 11:31 AM

    Gratified.

    ReplyDelete

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