DNA and mc have only 4 bases, and protein has 20 amino acids. How do these four bases determine the 20 amino acids in protein? If one base determines one amino acid, then four bases can only determine four amino acids, which is obviously not enough. The above speculation is only part of the process of cracking the genetic code. Later, through step-by-step speculation and experiments, scientists finally cracked the genetic code. On mc, three adjacent bases determine an amino acid, and every three such bases become a codon. Scientists have biased 64 genetic codons into the codon table below the city. So why do scientists speculate and experiment with three kinds of termination codes?
In the gobbledygook of human genes, if we want to understand this book, we must first understand the words that wrote it.
human gene
Then the words in the human gobbledygook are also called codons. In fact, we know that there are only four basic elements that make up the human body: adenine A, guanine G, cytosine C and thymine T.
Base complementary pairing
To write a genetic gobbledygook with these four basic elements, there must be different combinations, so as to understand it. In fact, this book is very simple, and it is full of these four letters, just like the following long string of characters composed of "ATCG":
Aacgtactactaccctctctcgatcgatggtctgccaggccttaggtgtgtcgtcgctgctacctgatttgcttacta ... Then we have to analyze it carefully, and it is definitely not a letter that represents a meaning, otherwise there are only four possibilities, that is, what A stands for, what T stands for, what C stands for and what G stands for; If two letters replace one meaning, there are sixteen possibilities, namely AT, TA, AC, CA, AG, GA, CT, TC, CG, GC, TG, GT, AA, CC, GG, TT. If three letters replace one meaning, there are sixty-four possibilities, so I won't list them here.
Basis group
In this case, the human gobbledygook consists of 64 codons, so this situation is the most practical. Among these 64 codons, there are some start codons and stop codons.
Complementary pairing of DNA genetic code
The human gobbledygook began as a dense book with 3 billion letters, and the number of letters in each person's genetic code has reached half of our world population. Many of such complicated contents are useless, but they are not helpful to our life activities. Among them, there are only about 654.38+10,000 genes, all of which are scattered in these 3 billion letters. So how do we identify them? We need to use start codon and stop codon. The initiation codon plays a role in releasing the initiation signal. When the human body's own reading mechanism encounters the initial codon, it will immediately start transcription and translation, which also shows that a long string of letters is the gene we want to read, and the three codons are transcribed and translated respectively until the stop codon ends.
Deoxyribonucleic acid
Some people may ask that there are only 65438+ 10,000 genes that are really useful. Why are there so many useless letters in human gobbledygook?
chromosome
This is about the ability to feel nature. In the process of evolution, human beings are always influenced by external environment, such as external radiation, virus destruction and their own variation.
At the same time, our bodies are constantly changing, which means that codons will mutate with a certain probability. If they are all useful gene sequences, it will probably have a great impact on our heredity and health. If there are a large number of useless genes outside the useful sequence, even if the genes are affected by the external environment, the mutation rate will not change, which can greatly protect the effective genes from harm, thus ensuring the stability of the genes, which is precisely the greatness of nature!