DR.TSUBOKURA'S RADIATION LECTURE VOL.176

Author: Masaharu Tsubokura M.D., PhD.

Editor: Yudai Kaneda

351　 DNA is a folded structure

30 October 2021

DNA is a huge dictionary of all the original blueprints that organisms need to live. In humans, there are about 3 billion of these four letters in a row.

　DNA exists as a set of two pairs, like a left and a right hand, and is structured like a twisted ladder. The ladder is not a rigid ladder made of aluminum or wood but more like a rope ladder used only for evacuating from high places. If these 3 billion rungs of the ladder were left open and extended, they would take up a lot of space. For this reason, the ladder is folded down to a small size in the organism’s nucleus. Specifically, many round ball-like proteins called histones are wrapped around this rope ladder, and DNA exists in a small folded form wrapped around these balls. We call this mass of rope ladders DNA, and the balls of histones are chromosomes. The name came from the fact that they are easily stained by certain pigments, but they are really a folded up, long piece of DNA.

352　 DNA replicates and cells multiply.

6 November 2021

DNA is a huge dictionary of all the original blueprints that organisms need to live. DNA is written with only four letters. In humans, these four letters are lined up in rows of about 3 billion. The structure is like a twisted ladder.

　The cells that make up our bodies divide and multiply as needed. DNA exists in the nucleus of the cell and is the original blueprint. A copy of the original blueprint is needed for the destination cell.　This is called DNA replication. The actual process involves pulling the ladder apart to the left and right sides and using each as a template to make the other. The right side of the ladder is used to make the left side of the ladder, step by step, to complete the ladder. Finally, the right side is used as a mold to make the left side, and the left side is used as a mold to make the right side, thus duplicating one original into two total.

　Many proteins are involved in this replication. Some are used to pull the ladder apart on the left and right sides, some are used to make the ladder’s rungs, and some are used to connect the rungs to each other. DNA replicates itself in the same way as when parts of the ladder are repaired after being damaged.

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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on 6 November and 30 October 2021 were reproduced for MRIC Global under the author's permission.