Scientists at the University of Washington have discovered how Neanderthal genes are expressed in modern day humans. These genes can influence several traits in humans, such as height, vulnerability to certain diseases, or how likely someone is to take up smoking.
These Neanderthal genes were gained through interbreeding that occurred between humans and Neanderthals more than 50,000 years ago. However, it is hard to identify how these genes influence humans today.
The difficulty in identifying how Neanderthal genes influence humans is given by the lack of living Neanderthals. They have died more than 40,000 years ago and DNA has been preserved in their remains, but any chemical signs of the genes are no longer there.
To create a picture of how these genes work, the researchers studied certain Neanderthal genes that were found only in some people. They used a huge database to identify those who had one copy of certain Neanderthal genes and compared them to those who had two copies of the genes.
As humans have two copies of each chromosome apart from the sex ones, they also have two copies of each gene that is carried by these chromosomes. The Neanderthal genes show variation in their expression, which contributes to phenotypic variation in humans.
For example, there is a Neanderthal gene that is associated with schizophrenia and it expressed differently in people who have one copy of the gene as compared to those who have two copies.
Also, the results showed that the genes of Neanderthal origin have a much lower form of expression than the human ones, since the Neanderthal DNA in them is not as compatible with human DNA as it the DNA in human genes is. In some cases, the Neanderthal genes might not be expressed at all.
Neanderthal genes have a low expression on the brain and testicles. That is because they might have a huge negative impact if they had a higher one. For instance, a higher expression in the testicles might have caused infertility.
The researches explain this phenomenon from an evolutionary point of view. They said that the dominant population was more likely have more relevant selection effects, while the smaller one was influenced by other factors. Also, hybridization might not have functioned so well in the evolution. However, these Neanderthal genes are present in many of us and they might have quite a big influence on our gene expression.
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