70 trillionth!How unique is your birth?

When you feel very small and insecure, remember how incredible your birth is.

01

As far as many accidents are concerned, we do not have accurate perception of the relative possibilities of various accidents. We are often afraid of unlikely, but ignore or underestimate more threats.

The bad judgment of human beings on the possibility of various events is also reflected in the possibility of our own presence as an individual. The probability of we died in animal attacks was insignificant, but the game games staged in parents' reproductive glands were already doomed, and the probability of we could be born was really minimal.

Some people may learn from their parents that their births are purely an accident, but the truth is that the birth of all of us is an accident. More importantly, the physical mechanism we live in is an extraordinary system formed by accident.

Imagine that there is a large group of meteors near a large planet in the solar system, about 100 million. Most meteors run on the track of throwing them to empty space, but a small cluster breaks out of the whole, and suddenly flew towards this large planet.

Over time, some of them will be close to the surface of the big planet, and then it looks like it has rebounded by the external atmosphere of the big planet. However, a meteor finally broke through the protective layer of the big planet, colliding with a large planet and released huge energy. The huge body of the big planet is constantly trembling and released a large amount of chemicals.

But this time, life did not end, but was born.

Are you a little puzzled? If these meteors have a head and a long tail, is it easy to understand?

They are human sperm, and that impact is the moment when the egg is fertilized, that is, a sperm penetrates a 30 times the outer layer of its size. Trends and release of chemicals are part of the severe physical and chemical changes of eggs. These changes prevent the process of combining eggs with other sperm and starting the process of embryonic development.

Only one sperm stands out from up to 100 million competitors, travels along the fallopian tube along the way, and finally successfully fertilizes the eggs. Fertilized eggs are a combination of two genomes, half of which chromosomes come from sperm and the other half from eggs. Speaking of which, tell you an amazing fact that no two fertilized eggs are exactly the same.

Yes, those who describe everyone how different they are, although they are a little boring, they do have some reason. Except for the twins of the ovulation, everyone's genes are unique, just like snowflakes!

You may be thinking: "Is this true? My eyes are like a mother, my nose is like a father, but the same is true of my brothers and sisters!"

Well, it is time to take a small test: If both parents contribute 23 chromosomes when they fertilize, how many genes do your parents may have a total of unique children?

Guess, 23? 46? 92?

Nothing. Give you a tip: the answer is more than 70 ... trillion. That is, after 7 followed 13 0.

02

Let's count how this number comes. The key to calculation is that we must figure out how many possible chromosome combinations are available. Humans have 23 pairs of chromosomes and a total of 46 chromosomes.

Among them, 22 has the same structure of chromosomes in boys and girls. They are called autosomal chromosomes, while the other two chromosomes X and Y are sexual chromosomes -boys have one x and one y; girls have two X X. Essence Generally, mature sperm and eggs include 23 chromosomes, so that the fertilized eggs have a complete 23 pairs of chromosomes.

In this way, everyone inherits half of the parents' chromosomes through the sperm of the father and the mother's eggs. And your father and mother have inherited half of the chromosomes from their parents.

This means that any chromosomes in sperm or egg cells are actually the result of two choices. These chromosomes are not exactly the same because they come from different ancestors. They will carry most of the genes of the selected DNA sequence.

Therefore, the number of combinations that the two chromosomes may be formed are 22 = 4, and the number of combinations that 3 chromosomes may form are 23 = 8, and so on. The possible combination of 23 chromosomes is 223, so the number of different combinations of sperm in the sperm is 8 388 608. The same is true for eggs.

It can be seen that the combination of sperm and eggs is the product of these two numbers, that is, 246 = 8 388 608 × 8 388 608 = 70 368 744 177 664, about 70 trillion, corresponding to 70 trillion different babies Essence

This is an astronomical figure. A man's testicles generate at least about 100 million sperm per day, so that at least 2 trillion sperm can be produced in his life.

On the contrary, women have already stored all the eggs they will produce at their bodies -about one or two million pieces, and in adolescence, the number of eggs in their bodies decreases to about 50,000 pieces. Because only one egg is usually discharged every month, the number of women controls the number of children in a range far below trillion.

The above calculation process shows that each of us is unique.

But in fact, this underestimates the potential number of unique children. This is because there are two other factors that affect the genetic process. The first factor is the genetic reorganization process.

When chromosomes are paired during the formation of sperm and eggs, they can be reorganized and exchanged fragments with each other. The new chromosomes produced are mixtures of the parent chromosomes (see the figure below). Since genetic reorganizations can occur almost any position on chromosomes and occur on an average of each pair of chromosomes, the actual number of eggs and sperm with different chromosomes is far greater than 8 388 608.

Note: When the chromosomes are paired in the formation of sperm or eggs, they can be reorganized with each other. In this way, each chromosome is a mixture composed of two chromosomal genetic information. From the perspective of the picture, it is like mosaic patterns.

In addition, there is no change in the genes of both parents, which occurs during the formation of eggs and sperm. As mentioned earlier, each sperm or egg has 20-35 new mutations, which occur randomly in the entire genome. Therefore, the number of sperm and eggs containing different genetic genes is astronomical.

Thanks to these 4 random mechanisms: the chromosome is randomly copied into sperm and eggs, the chromosomal fragments are exchanged randomly, new mutations occur randomly, and a lucky sperm successfully combines with a certain egg. The unique combination of chromosomes, genes and mutations.

Each of us is unique and accidental -a collision of a sperm with unique genes and an egg with unique genes.

Recommended reading

How does it shape this world and humans itself? In this book, the evolutionary biologist Sean B. Coroel starts with new discoveries from many fields such as ancient biology, geology, evolutionary biology, genetic science and other fields. Many interesting empirical evidence, show you the power of "accidental".

At the same time, Corol's cocoon clarifying the problem that troubled Darwin's "mutation and natural selection, which one is the real inventor" and helps you clarify the relationship between mutation, natural selection, adaptation, and adaptation, and as well as, as well as, as well as, and adapting, and as well as the relationship between the mutation, adaptation, and the adaptation, and the adaptation, and the adaptation, and the adaptation, and the adaptation, and the adaptation, and the adaptation, and the adaptation, and the adaptation, and The role played in the process of evolution.

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