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Why is Neanderthal Genetic material Found in only Small amount in Genomes of Modern Humans?

The scientists estimated that these gene variations were able to persist in Neanderthals because Neanderthals had a much smaller population size than humans

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FILE - A model of an adult Neanderthal male head and shoulders by artist John Gurche on display in the Hall of Human Origins in the Smithsonian Museum of Natural History in Washington, D.C. VOA
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New York, November 9, 2016: Neanderthal genetic material is found in only small amount in the genomes of modern humans because, after inter-breeding, natural selection removed large numbers of weakly deleterious Neanderthal gene variants, says a study.

Humans and Neanderthals inter-bred tens of thousands of years ago, but today, Neanderthal DNA makes up only one to four per cent of the genomes of modern non-African people.

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“For a while now we have known that humans and Neanderthals hybridised. Many Europeans and Asians – along with other non-African populations – are the descendants of those hybrids,” said Ivan Juric from the University of California, Davis in the US.

“Previous work has also shown that, following hybridisation, many Neanderthal gene variants were lost from the modern human population due to selection. We wanted to better understand the causes of this loss,” Juric noted.

To understand how modern humans lost their Neanderthal genetic material and how humans and Neanderthals remained distinct, the researchers developed a novel method for estimating the average strength of natural selection against Neanderthal genetic material.

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They found that natural selection removed many Neanderthal alleles from the genome that might have had mildly negative effects.

The scientists estimated that these gene variations were able to persist in Neanderthals because Neanderthals had a much smaller population size than humans.

Once transferred into the human genome, however, these alleles became subject to natural selection, which was more effective in the larger human populations and has removed these gene variants over time.

“Our results are compatible with a scenario where the Neanderthal genome accumulated many weakly deleterious variants, because selection was not effective in the small Neanderthal populations. Those variants entered the human population after hybridisation,” Juric said.

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“Once in the larger human population, those deleterious variants were slowly purged by natural selection,” Juric noted.

These findings, published in the journal PLOS Genetics, shed new light on the role of population size on losing or maintaining Neanderthal ancestry in humans. (IANS)

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Research Yields Possible Blood Test for Cancer

The test was most successful with ovarian cancer, followed by liver, stomach, pancreatic, esophageal, colorectal, lung and breast cancers.

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Scientists have found a way of detecting cancer through blood tests. IANS
Scientists have found a way of detecting cancer through blood tests. IANS
  • Scientists have developed a blood test which can detect cancer
  • This blood test can detect eight types of cancer
  • They have developed a way of detecting DNA which comes specifically from cancer

Scientists at Johns Hopkins University (JHU) are reporting progress in developing a blood test to detect eight types of cancer at an early stage, including some of the most deadly ones that are difficult to detect with existing screening tools.

In a study published Thursday in the journal Science, JHU scientists examined how well their experimental test detected cancer in people already diagnosed with the disease.

Also Read : How broccoli can help keep colorectal cancer away 

This blood test can detect 8 types of cancers. Pixabay
This blood test can detect 8 types of cancers. Pixabay

In blood samples from more than 1,000 patients already diagnosed with cancer, the test detected the cancer in about 70 percent of the subjects.

Nikolas Papadopoulos, a professor of oncology and pathology at Johns Hopkins Sidney Kimmel Cancer Center, said the test is noninvasive.

“All [patients] have to do is give a little bit of blood,” he told VOA. “What we detect is DNA, which is the genetic material that is present in all of our cells, but we have developed a method to detect DNA that comes only from the cancer cells.”

Scientists have been focused on liquid biopsy tests which look for mutated DNA that floats freely in the blood and in cancer-related proteins to try to find cancer before it spreads. They focused on cancers for which there is little or no early-screening process — the ones that are often serious enough to be deadly by the time they are detected.

“That’s one of the tricks that cancer plays on us,” Papadopoulos said. “It grows inside of us and we feel fine until we start having something like a pain or a cough or something like that. And many times, it’s too late.”

Also Read : Alcohol can be linked with seven types of Cancer

This test detects DNA which is specifically formed due to cancer. sites.bu.edu
This test detects DNA which is specifically formed due to cancer. sites.bu.edu

The test was most successful with ovarian cancer, followed by liver, stomach, pancreatic, esophageal, colorectal, lung and breast cancers.

“This study that’s just published, it’s the first step,” Papadopoulos said.

He said a larger study is under way, with a pool of thousands of people. Unlike the earlier study, which dealt solely with patients already known to have cancer, the new group makes up a more representative sample of the general population — that is, most do not have cancer, at least not that has been diagnosed.

“The new study is different in that it simulates what is going to be the population that this test will be applied to,” he said. “And hopefully, we will get good results.” VOA