Detailed analysis of the genetic structure of sperm could help scientists unlock clues to male infertility, claim researchers.

A team of experts - including some from Leeds - has mapped out a 3,000-part genetic sequence from a single sperm from an apparently healthy, fertile man.

Now there are plans to compare this as a benchmark to the sperm of infertile men - and hopefully reveal common differences which help unravel the reasons behind the failure.

Every cell in the human body is constructed from a blueprint contained in DNA contained in the nucleus.

However, this study, published in the Lancet medical journal, focused on other genetic material in the sperm cell - called messenger RNA (mRNA).

There is still plenty of debate as to the precise function of this material, which may simply be left over from the creation of the cell in the testicle, but some scientists believe it may play a key role in enabling the sperm to fertilise an egg and produce an embryo.

It is possible that this mRNA helps "energise" the embryo shortly after conception and is vital to its success.

Male mystery

While much is understood about the causes of female infertility, one in two cases of infertility involves problems with the male, and there is far less knowledge about the causes of this.

Often, it is the quality of the semen - and the relative motility of the sperm themselves - that is the only guide to the chances of fertilisation during IVF.

The researchers are hoping that their "mini-genome" will provide the "gold standard" for future studies.

In theory, the technology used to map mRNA could one day be used to screen sperm for the cells most likely to produce a healthy embryo.

Professor Chris Barratt, a researcher into male fertility at the University of Birmingham, told BBC News Online: "This will help us get to the heart of what is wrong in an infertile man.

"It still isn't clear whether mRNA has any relevance to the problem - so this should be pretty useful in helping us find out."