When studying living things, we often hear about DNA. It seems that all known living things on Earth have DNA, which is also called the basic blueprint of life and records and stores the genetic information that forms that living thing. DNA is a polymer called deoxyribonucleic acid, and in the nucleus of a human cell, which is 5 to 10 μm in size, there are 46 chromosomes, each about 1 μm thick, in pairs of 23 from the father and mother, and DNA is stored by wrapping around each chromosome and folding it. The total length of DNA in the 46 chromosomes is said to reach 2 m, and it is an amazing folding technology to fit 2 m into 10-5 m.
DNA contains about 6 billion pairs of base pairs, such as A (adenine) and T (thymine), G (guanine) and C (cytosine). If we convert this to bit data of 0 and 1, one piece of DNA would contain about 6 billion bits, or about 0.7 GB, which is about the size of one CD. This information density is about a million times that of a hard disk drive. It’s amazing that all cells contain this amount of information.
It seems strange that every cell in an organism contains its own blueprint, but it may be effective in preventing information from being lost. From another perspective, it is also a little strange that the blueprint for a human being fits on a single CD.
The part of DNA that creates the blueprint for proteins is called a gene, and humans have about 20,000 of them, with each gene being made up of 1,500-2,000 base pairs and accounting for 1-2% of the total DNA. There are still some parts of the genome that we don’t know about. Comparing the genetic commonality between humans and other organisms, it seems that 96% of genes are the same as chimpanzees, 90% are the same as cats, 85% are the same as mice, and 60% are the same as flies, chickens, and bananas. As organisms, we are quite different, but we have more in common than we thought.
https://www.businessinsider.jp/article/165064
Also, it seems that genes have an on/off switch, so even if people have the same DNA, if there are differences in the parts that are expressed, their physical constitutions will be different. I had the impression that DNA and genes are determined by birth, but there are also parts that change due to acquired factors.
https://spap.jst.go.jp/asean/news/210603/topic_na_04.html
We have a strong image of DNA being shaped like a double helix, but upon further investigation, it appears that there are various other shapes. In addition to normal DNA (B-type DNA), there is a type of DNA that is zigzag and left-handed (Z-type DNA) that exists under high salt concentrations. So not all DNA is right-handed. There is also A-type DNA, which is slightly larger in diameter and shorter than B-type DNA.
In addition, although DNA is composed of the four bases ATGC, there is DNA (Z genome) that uses Z (2-aminoadenosine) instead of A. There are 200 species of bacteriophages (viruses that infect and replicate in bacteria and archaea) that have DNA composed of ZTGC.
https://www.newsweekjapan.jp/stories/world/2021/05/z-2_1.php
And it seems that DNA can take the form of not only double helix, but also triple helix and quadruple helix. There is also something called cross DNA. DNA seems to be a system common to all living things, but as living things are diverse, the DNA that serves as their blueprint is also diverse. Living organisms are complex, functional, and mysterious systems. DNA is amazing. Life on Earth is amazing.
