The male Y chromosome has finally been unlocked

Human geneticists announced more than 20 years ago that the working version of genetic mapping is ready, in July 2001. In fact, only 90 percent of our genes had been mapped.

A generation later, in 2021, the scientific community reported that the human genome has been read through. Yet something essential was still missing: a man.

The legacy presented was indeed that of a woman. It consisted of 22 normal chromosomes and a pair of XX chromosomes.

The package still lacked a complete reading of the man’s small Y chromosome.

in a person there are usually 22 pairs of chromosomes and two sex chromosomes, either chromosome pair XX or XY.

The Y chromosome produces male characteristics in the human embryo. One gene of the Y, sry, codes for a protein that controls testicular growth. The same gene also controls the formation of sperm.

Now The Y chromosome has been mapped and read through. The data was compiled from the genes of 43 men. 23 of them come from Africa, the rest from other continents.

The researchers report their findings in two in the article In the journal Nature.

In the past, so little genetic information had been gathered about the Y chromosome that it could not give a complete picture of the variants, the gene forms, of the Y genes.

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The Y chromosome is unlikely to disappear, although some geneticists have considered such a possibility.

on the Y chromosome on 693 genes, of which 106 encode proteins for the cell. Genes have a total of 62,460,029 DNA base pairs.

That’s more than 30 million base pairs more than reference genome in GRCh38. It is the “basic genome” that has been constantly updated over the years as genetic research has progressed.

Millions of base pairs make up the double-helix “ladder” of the hereditary DNA strand, i.e. DNA.

The Y-chromosome seems to collect repeated DNA sequences, like long palindromes.

It is impossible to tell from the small pieces whether they are written text on the front or on the back. Geneticists call them tilke dna.

“The Y chromosome is full of large areas where the same sequences of DNA blocks are repeated over and over again and change only a little. It made reading through Y challenging,” says New Scientist -in leaf Sergey Cornerwho works today Oxford Nanopore in a company called

Y chromosome the size varies from person to person to almost double due to the tilke. We don’t know why some people have more tilke than others, says the heredity doctor Kirmo Wartiovaara from the HUS group. He is also a stem cell researcher at the Faculty of Medicine of the University of Helsinki.

As when putting together a puzzle, the ensembles of pieces that look the same are the most difficult. Usually they can only be put in their right places at the end of the puzzle. The same applies to the human gene map.

Of use in assembling the final stage of the puzzle came the Oxford Nanopore company. The technology it developed reads the sequence of a single DNA molecule as it passes through a small hole.

The technique produces pieces for examination that contain millions of letters of DNA, instead of being a few hundred letters long.

This is how the new technology helped in mapping the Y chromosome, says one of the lead authors of the second research report Charles Lee. Lee is a professor at the Jackson Genomic Medicine Laboratory in Connecticut.

The DNA blocks were arranged in different ways in the Y chromosomes of the men who participated in the study, but they always appeared in the same ratio, the ratio of one to one, says website Live Science.

“I think this permanent relationship suggests that these regions of the chromosome have some significance that is not yet known,” says Lee.

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“It’s interesting that the Y and X chromosomes were once, a long, long time ago, the same.”

Studies suggest that episodes may have even contributed to the evolution of the human brain.

“The Y chromosomes of the subjects in different human groups diverged from each other sometime 180,000 years ago. Previous studies covered ‘only’ 50,000–60,000 years of evolution,” says Wartiovaara.

“It is interesting that the Y and X chromosomes were once, a long time ago, the same. They still have a small share of the same genes, in so-called par episodes,” says Wartiovaara.

The par periods of the Y-chromosome change much faster than those of the X-chromosome, but we can only guess the reason.

Recurring The DNA sequences are therefore not useless “junk DNA”. Geneticists have been talking about tilke-dna for a long time.

At the beginning of the millennium, geneticists used the word pair “junk DNA” to describe the regions of the DNA strip that do not directly code for protein in the cell.

Some unknown human Y sequences were previously thought to be, for example, bacterial DNA, which would have contaminated human samples, says the website Science Alert.

Some geneticists didn’t even try to sequence Y at first. They considered the chromosome to be a “graveyard” for those genes that did not matter. They were even destined to disappear in evolution.

In the human reference genome GRCh38, for example, “the Y chromosome was just pushed aside at first,” says Lee.

The sound in the clock has since changed. The Y chromosome is hardly disappearing.

“Now the holes have been filled and we have an accurate picture of the Y chromosome,” says one of the lead authors of the second study Adam Philippy.

“Like watching high-definition television. The work made the picture very clear,” says the geneticist from the University of Leicester Mark Jobling In the journal Science. He was not involved in the investigations.

Correction 12.9. at 10:30 a.m.: There are a total of 62,460,029 DNA base pairs in genes, not 62,460 29, as was stated in the story at the beginning.

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