Our bodies are very keen on making DNA. If not, we can’t survive. However, DNA itself is lifeless. It’s an organic macromolecule and an inactive chemical inert molecule. That’s why DNA can be extracted from the dried blood or semen stains for a long time during the murder scene investigation, as well as from the ancient Neanderthal DNA was extracted from the skeletons of Tete people.
This kind of material is mysterious and low-key, which can be described as lifeless. It took scientists so long to realize that they are the core of life.
As an entity, DNA existed for more time than you could imagine, but it was not discovered until 1868-1869 by a Swiss scientist Mitchell who worked at the University of dibingen in Germany.
Mitchell once used a microscope to study the pus in a surgical bandage, and found a substance in the nucleus that he did not know, and called it nuclide. But at that time, Mitchell only noticed their existence, but he didn’t think much about them, so he didn’t pay attention to them.
In the half century after that, it was generally believed that this material, later known as deoxyribonucleic acid, played a negligible role in genetics at best.
Because its structure is very simple, there are only four components in total, and life is extremely complex. At that time, scientists’ cognition was very limited, so they thought that DNA was useless, just a kind of material to stay quietly in the nucleus, and the material needed for life could only exist in the protein of the nucleus.
But there are two things about DNA that people can’t take lightly.
First, there is a large number of DNA. Almost every cell nucleus contains nearly two meters of DNA, which shows its importance to cells. In particular, DNA always appears in experiments, especially in pneumococcal and bacteriophage experiments. But this only shows that the importance of DNA has been greatly underestimated by our predecessors.
Second, there is evidence that there is a relationship between protein production and DNA, which is crucial for life. But what puzzled people at that time was that proteins were definitely generated outside the nucleus. If they were controlled by DNA, they were a little far away from DNA. No one could figure out how DNA transmitted information to proteins.
But as we all know today, this is actually with the help of a substance called ribonucleic acid, that is RNA, which plays the role of translation between the two. That is to say, DNA and protein do not speak the same language, which is a famous strange thing in biology.
In nearly 4 billion years, they are the two most important actors on the stage of life, but they use two incompatible codes. They need RNA as a communication medium. With the help of a chemical substance called ribosome, RNA interprets the information in DNA to protein, and makes protein take it as an action instruction.
Happily, in 1909, Thomas Hunt Morgan began to wrestle with fruit flies. He and his team wanted to achieve characteristic variation in fruit flies, such as lack of arms and legs, a pair of wings and so on. So they crossed millions of fruit flies.
Because Drosophila flies are small and eat less, they don’t need much money and are easy to raise. It takes only ten days from egg to adult, and there are only four groups of chromosomes, so the research is relatively simple.
They carried out a variety of experiments on fruit flies, such as chemical treatment, high temperature treatment, radiation, X-ray irradiation and so on. However, despite such setbacks, they still did not get the results they wanted.
When Morgan was about to give up, he found the first mutation in the fruit fly. One male fruit fly had white eyes.
Later, after a series of reproductive experiments, Morgan confirmed in 1911 that the gene for white eye was located on the X chromosome, which was a key step. In 1915, Morgan’s laboratory discovered 85 kinds of genetic mutations. However, the problem has not been completely solved. When people go deep into the more complicated next level of biology, they find that it is difficult to isolate genes and the DNA that constitutes genes, and it is also difficult to explore the specific role.
Until 1933, when Morgan won the Nobel Prize, there were still many researchers who didn’t believe in the existence of genes. What are genes? Are they real existence or pure imagination?
Morgan said there was no consensus at the time. You may be surprised, because in our view today, genes play such a basic role in cell activities. At that time, many scientists doubted its authenticity and were reluctant to admit it.
But in fact, this is not surprising, because the group of scientists is exactly the group with the most questioning spirit. It is precisely with this kind of harsh questioning that we can ensure that the knowledge we know today is reliable and can be directly used by future generations.
For people in Morgan’s time, it was ridiculous to take a gene from the body and study it.
What we can be sure is that some substance related to chromosome dominates the cell reproduction. Finally, a team made a breakthrough in 1944 by fusing a non pathogenic bacterium with foreign DNA, thus making the bacterium produce permanent pathogenicity.
Finally, DNA was deciphered by four young scientists in 1953. They believed that as long as they knew the shape of DNA molecules, they could understand how they worked. The later results also proved that their idea was right. Since then, the molecular model of DNA double helix structure has been put forward by them.
Do you think the course of DNA exploration is very bumpy? Yes, science is rising in constant geological doubts. What do you think about DNA? Welcome to comment area.