Men have one copy, women have two, though scientists have prolonged undetermined over since a tellurian X chromosome mostly contains genes that are active in a tiny series of tissues. Now, a group of researchers led by a University of Bath investigate a expansion of this X chromosome has detected since it contains such an surprising reduction of genes.
In humans, males have XY chromosomes, females have XX though usually one of these is active, definition that both sexes usually have one active duplicate of a X chromosome.
Scientists detected in 2002 that a X chromosome is surprising since it contains really few of a many critical genes indispensable for elementary dungeon duty – dubbed “housekeeping” genes.
Now a team, a partnership between researchers during a University of Bath and Uppsala University, along with members of a FANTOM consortium, have found out why.
They analysed a world’s largest collection of information on gene activity (expression) and looked during how activity on a X chromosome compares with that on other chromosomes.
In a paper published in a biography PLoS Biology, they found that a rise turn of gene countenance on a X chromosome was underneath half that of other chromosomes where we have dual functioning copies.
It takes two
The investigate was led by Professor Laurence Hurst, Director of a Milner Centre for Evolution formed in a Department of Biology Biochemistry during a University of Bath.
He explained: “Since we showed that X-linked genes tend to be comparatively hankie specific over a decade ago, a reason as to since a X chromosome is so peculiar has bugged me.
“In a end, we have found a answer to be utterly simple. Whereas many chromosomes work in pairs, definition there are dual copies of any gene in each cell, in contrast, we usually have one active duplicate of a X chromosome.
“This means it is not sufferable for rarely active genes to be on a X chromosome. Housekeeping genes tend also to be rarely active – they usually couldn’t tarry on a X.”
The group also identified that genes have changed from a X to a other chromosomes over evolutionary time and those that have left a other way.
They found that those genes that have migrated onto a X chromosome have many reduce rise rates of countenance that those creation a retreat trip.
Hurst explained: “It’s a bit like trade on a bustling highway – a highway with dual lanes can have a lot some-more and faster trade on it than a singular line highway.
“A effect of carrying a singular chromosome is that, like a one line road, there will be gene countenance trade tailbacks on a X chromosome generally during rise periods. Hence a X chromosome will not be a sufferable home for a many rarely voiced genes.”
The investigate also found that, distinct those found on other chromosomes, a some-more rarely voiced genes on a X chromosome were reduction disposed to augmenting their countenance turn over evolutionary time.
Senior author Lukasz Huminiecki of Uppsala University commented: “This fits with a trade analogy as, if there is a tailback, it is tough to boost a speed of a cars on a road.”
The group also found that there has been an evolutionary exodus of genes that are rarely voiced during rise times from a X chromosome, suggesting these genes can't duty on this chromosome due to a fact there is usually one active copy. For example, genes that are active in tissues such as a pancreas that secretes a vast series of protein hormones, are noticeably singular on a X chromosome compared to a non-sex chromosomes.
Huminiecki added: “With a conspicuous fortitude of a FANTOM gene countenance data, we have shown that nothing of a before explanations resolves entirely a mysteries of a X. For example, if we bar genes voiced in tissues that are found in usually one sex or are concerned in creation sperm, a residue still have comparatively tissue-specific activity.”
The work has implications for new medical treatments such as gene therapy as it suggests that deputy genes should not be extrinsic into a X chromosome since trade tailbacks might border a border to that a gene can be expressed.
Source: University of Bath