Researchers have just taken a big move to decipher the entire human genome

Researchers have just taken a big move to decipher the entire human genome

At the conclusion of its 13-year term in 2003, the Human Genome Project mapped nearly 90% of its genetic code. Many of the other pieces have been hard to decipher, however.

Over the course of the years, DNA reading capacity has increased, slowly closing these holes and researchers are drawing a full image of the genome. Yet some 100 or so areas, including some parts of the chromosome X, are still incomplete.

Researchers have just taken a big move to decipher the entire human genome

Now, for the first time, researchers have created a map of the X chromosome from end to end. This achievement was published on July 14 in Nature journal, which can help scientists understand a variety of genres.

Mapping these regions into the X chromosome and elsewhere is a formidable task for researchers as it includes several repetitive fragments of DNA. Such fragments can repeat thousands or even millions of bases of DNA letters.

Karen Miga, a DNA biologist at the University of Californa, Santa Cruz and author of a new article tells OneZero “The assembly or the collection of such works was unlikely until recently,”

Researchers have employed sophisticated sequencing technologies to decipher the X chromosome because most individuals have at least one. Genetically-born females generally have X chromosomes, while genetically-born males normally have an X and a Y.

“To have a link with a large number of traits and disorders, the X chromosome is of interest in human medical genetics and genomics,” Miga says. The X chromosome, for example, is concerned with blindness, muscle dystrophy and haemophilia of Duchenne.

“Assembling or putting these pieces together was impossible until only recently.”

Miga worked on the technique called fast-read sequencing for Adam Phillippy, an investigator at the National Human Genome Research Institute who can read long stretches of DNA base in one moment.

The human genetic code is incredibly long — about 6 billion bases — and all of these bases can not be translated by DNA sequencing machines at once.

Instead, researchers need to split the genome into hundreds of smaller pieces and study the smaller pieces one by one. They have to put them together until this is completed.

Scientists were able to read only approximately 500 letters during the first stages of the human genome project. Sequencing technology became more specific in the mid-2000s, but it reduced the time for reading DNA to some 100 to 200 letters at a time.

In 2010, new technology was introduced and about 10,000 bases could be read at once. For older sequencing technologies, these repeated DNA sections created small, almost identical pieces, which gave few hints as to how the pieces can be mounted.

Now, sequencing advances mean that certain computers can simultaneously read about 100,000 or more bases. The X chromosome from a similar cell group with two identical X chromosomes was analyzed using two separate instruments.

Phillippy and his team then applied a new computer program to assemble the many segments they created.

On the X chromosome, a void at the middle of the chromosome and a number of units of the genes were filled. There were no great surprises for the researchers — for starters, there were no new, undiscovered genes.

Yet they have discovered a large number of variations in these repetitive genome sections. These contain individual DNA-letters which are copied, transferred or reversed and can be exchanged, removed, added or larger pieces of DNA. It is understood that these variations contribute to genetic illnesses.

Further research into these previously unmapped genome areas may open up new genome regions where researchers are able to identify potential interactions between these variations and genetic diseases of unknown origin.

“You can turn a blind eye to some of the richest sequences of human diversity and some sequence of diversity you are not looking at, which can be related to a disease in a way we have never been able to research before,” says Miga.

With the expectation of eventually collecting the first full human genome, the researchers turn to other missing chromosomes.

Researchers have just taken a big move to decipher the entire human genome

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