CATDOLL : CATDOLL: Why are my fish getting smaller and smaller?

Why are my fish getting smaller and smaller?

Because he is very small. Or he doesn't want to grow up.

Most prokaryotes have circular DNA, no telomeres, and their DNA does not shorten. So why don't they live forever?

I heard that the Turritopsis dohrnii can return to its "young age" after reproducing offspring. In the absence of environmental resistance from natural enemies, it can achieve immortality. I am at a loss for words, so I found this on the Internet: You should know that humans have telomeres and telomerase: Telomeres are short, multi-repeated non-transcribed sequences and some binding proteins that form a special structure. In addition to providing a buffer for non-transcribed DNA, they can also protect the ends of chromosomes from fusion and degradation. They play an important role in chromosome positioning, replication, protection and control of cell growth and lifespan, and are closely related to cell apoptosis, cell transformation and immortalization. When a cell divides once, the telomere of each chromosome will gradually become shorter. A part of the gene that constitutes the telomere, about 50 to 200 nucleotides, will not be completely replicated (lost) due to multiple cell divisions, so that the cell stops its function and no longer divides. Therefore, severely shortened telomeres are a sign of cell aging. In some cells that require an infinite replication cycle, the length of the telomere is retained after each cell division by the special DNA polymerase-telomerase that can synthesize telomeres. Therefore, as long as there is a continuous supply of telomerase, human cells can divide indefinitely, never age, and can live forever without disease... Let's talk about the questioner. Of course, activating the immortality gene is a good thing for individuals, but it will make the aging of the population more and more serious, and the burden on each young person will become heavier, because they have to support the immortal elderly who have doubled. Also, if they are very old, it is inconvenient to get injections, infusions, and surgeries if they have diseases. Therefore, there should be many people suffering from illness. In addition, if everyone is immortal, the world population will increase, which will have a very bad impact on resources and the environment. These are the advantages and disadvantages of the immortality gene. It seems that the disadvantages outweigh the advantages. Therefore, it is better to supply telomerase continuously, because with telomerase, cells will not age, and even if they grow bigger and bigger, they will still remain young forever. Therefore, no matter how old you are, you can still go to work and do things, and you will not become a burden to society... But the immortality gene is different. Although people are immortal, they will still get older and older, and finally become a burden to society, and there is no meaning in living. Therefore, it is better to use telomerase. The immortality gene has more disadvantages than advantages. Telomerase can be cultivated in large quantities using E. coli, but scientists cannot use humans for experiments, nor can they keep the subjects alive until they live forever (in order to see the effect, they must keep the subjects alive until they live forever, which is really embarrassing...). The key still depends on current and future technology...