Home / Science / "The Heart of Darkness of the Human Genome" – Suspend Neanderthal Influence

"The Heart of Darkness of the Human Genome" – Suspend Neanderthal Influence

  Neanderthal vs Human

"It is the heart of the genome of the genome, we warn students not to go there," said Charles Langley, a professor of development and ecology at the University of California, Davis. Geneticists who explore the dark heart of the human genome have discovered large pieces of Neanderthal and other old DNA. The results open new ways of studying how chromosomes behave during cell division and how they have changed during human development.

The central area of ​​chromosomes, centromers, contains DNA that has survived largely unchanged for hundreds of thousands of years, researchers at UC Davis and Lawrence Berkeley Laboratory have found. Some of this DNA comes from Neanderthals or other relatives or ancestors of humans from before modern humans migrated from Africa.

  The central part of chromosomes, the centromer,

Centromers are located in the middle of chromosomes, the clamped "waist" in the image of a chromosome from a biology manual. Centromers anchor the fibers that pull the chromosomes apart when the cells divide, which means they are very important in understanding what happens when cell division goes wrong, leading to cancer or genetic defects.

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But the DNA of the centromeres contains many repetitive sequences, and researchers have not been able to correctly map this region. "It's the heart of the genome of the genome, we warn students not to go there," says Langley, senior author on a paper describing the work published in a forthcoming issue of eLife magazine.

Langley and colleagues Sasha Langley and Gary Karpen at the Lawrence Berkeley Laboratory and Karen Miga at UC Santa Cruz reported that there could be haplotypes – groups of genes inherited in human development – that extend over much of our genomes and even over centromeres.

This is because the centromer does not participate in the "crossover" process that occurs when the cells are divided to form sperm or eggs. During the crossing, paired chromosomes extend side by side and their limbs cross, sometimes cut and split DNA between them so that genes can be mixed. But transitions fall to zero near centromere. Without mixing in each generation, centromeres can preserve very old DNA stretches intact.

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The researchers searched for hereditary simple nucleotide polymorphisms – hereditary changes in a single letter of DNA – that would allow them to map haplotypes in centromeres.

They first showed that they could identify centromeric haplotypes, or "perhaps," in Drosophila fruit flies.

That finding has two consequences, Langley said. First, if researchers can distinguish chromosomes from one another with their centromers, they can begin performing functional tests to see if these differences have an impact on which piece of DNA is inherited. For example, during egg formation, four chromatids are formed from two chromosomes, but only one makes it to the egg. So researchers want to know: Are some centromere haplotypes running more often? And are some haplotypes more likely to be involved in errors?

Second, researchers can use centromere to watch ancestry and evolutionary descent.

When one came to human DNA, the researchers looked at centromere sequences from the 1000 Genom project, a public directory for human variation. They discovered haplotypes spanning the centromere in all human chromosomes. Half Million Years Haplotypes In the X chromosome of these genome sequences, they found several large centromeric haplotypes representing lines that stretched back half a million years. In the genome as a whole, most of the diversity of African genomes is seen as consistent with the recent spread of people from the African continent. One of the oldest centromere haplotype lines was not transported by the early emigrants.

In chromosome 11, they found highly diverged haplotypes of neanderthal DNA in non-African genome. These haplotypes deviate between 700,000 and a million years ago, around the time the ancestors of Neanderthals shared from other human ancestors. The 12 chromosome of the chromosome also contains an even more ancient, archaic haplotype that appears to be derived from an unknown relative.

This Neanderthal DNA on chromosome 11 can affect the differences in our sense of smell to this day. The cells that respond to taste and smell carry smelling receptors triggered by specific chemical signatures. People have about 400 different genes for smelling receptors. Thirty-five of these genes reside within the chromosome 11 centromeric haplotype. The neanderthal centromeric haplotypes and a second ancient haplotype account for about half of the variation in these olfactory receptor proteins.

It is known from other works that genetic variation in smelling receptors can affect the sense of taste and smell, but the functional effects of

The Daily Galaxy via UC Davis

Image Credit: Thanks to Philipp Gunz (CC BY -NC-ND 4.0) [Variation i den här studien] 19659027] (function (d, s, id) {
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