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ann re: 'athletic prowess' gene, page-2

  1. 2,129 Posts.
    re: ann 'athletic prowess' gene There is a differing of opinions as to the benefit of this particular test, including some from North's team.


    http://www.newscientist.com/news/print.jsp?id=ns99994092





    Seaking_______________linking





    19:00 27 August 03

    Exclusive From New Scientist Print Edition.

    A specific gene linked to athletic performance has been discovered by Australian sports scientists. The announcement comes as elite athletes vie for glory at the World Athletics Championships in Paris, and reopens the debate about whether top athletes can be screened and nurtured from birth.

    The gene comes in two variants. People with one variant are predisposed to become sprinters. Those with the second are more likely to excel in endurance events. This is the second gene to be shown to confer athletic ability. The first, angiotensin-converting enzyme, or ACE, makes an enzyme which influences how efficiently our muscles burn oxygen, and the rate at which some muscles grow (New Scientist print edition, 23 May 1998).

    The gene discovered by the Australian team is called alpha-actinin-3, or ACTN3. One version, the R allele, makes actinin, a protein found only in fast muscle fibres. These fibres help to produce the explosive bursts of speed and power that sprinters need. The other allele, called X, does not produce actinin-3.

    Winning Formula.

    The researchers studied the genetic profiles of over 300 athletes, 50 of whom had represented Australia at Olympic or international level at various sports. They found that 95 per cent of elite sprinters possessed at least one copy of the R allele while 50 per cent had two copies, one inherited from each parent ( American Journal of Human Genetics, vol 73, p 627).

    But just 76 per cent of endurance athletes possessed an R allele, with only 31 per cent inheriting both (see graphic). Out of over 400 controls taken from the general population, 82 per cent had one R allele and 30 per cent had two Rs.

    Sprint Olympians.

    Some people inherit two X alleles, and so do not make actinin at all. Just 5 per cent of sprinters had two copies of the X allele, compared with 18 per cent of the controls. "No female elite sprinters or sprint Olympians were XX," says team leader Kathryn North of the Institute of Neuromuscular Research at the Children's Hospital at Westmead, Sydney.

    However, when it came to endurance runners, a larger than average proportion, 24 per cent, had inherited the XX combination and so were unable to make actinin-3. "I hypothesise that absence of alpha-actinin-3 means that an individual's muscles are more 'slow' in character, and better suited for endurance activities," says North.

    The exact role of actinin-3 is unclear. "It may confer a greater capacity for the absorption or transmission of force during rapid, forceful contraction," North says. Her team are conducting lab and animal studies to find out.

    North's team, which includes researchers from the Australian Institute of Sport, claims that ACTN3 is particularly significant because actinin forms a part of the musculature, whereas ACE only codes for an enzyme. "Although at least 73 genetic [regions] have been associated with fitness and performance, ACTN3 is the first structural skeletal muscle gene for which such an association has been found," she says.

    Talent Scouts.

    However, this interpretation is disputed by Montgomery, whose team at University College London discovered ACE and now says it has unpublished evidence pointing to a third gene that predisposes for enhanced physical performance.

    ACE also has a direct impact on musculature, Montgomery says, because it influences whether "fast" or "slow" muscle fibres are laid down. And like ACTN3, ACE comes in two main inherited forms: the I form that favours endurance and the D form that favours sprinting.

    Montgomery dismisses the notion that talent scouts could genetically screen for future elite athletes. "It's very unlikely there will be one gene that is a major indicator of performance." He says many factors influence sporting success, including body size, fibre type, metabolic efficiency, lung volume, psychological make-up and sheer application. "It's easier to go out with scouts and choose kids who are performing well."

    Members of North's team accept there is something in this. "Being an elite athlete is not entirely dependent on ACTN3. It is still highly contentious whether we can use genetic markers to predict performance at all."

    Positive Discrimination.

    "The research has not been done," says Jason Gulbin, who coordinates scouting activities for Australia's Institute of Sport. "But if we find a genetic profile has a useful predictive function, then I prefer to consider how this might be used to positively discriminate".

    Multi-talented athletes only have a short time in which to decide which sporting areas will suit them best, so knowing their genetic make-up could help them make informed decisions about which discipline to focus on.

    He rejects the idea that genetics would make sport even more elitist. "Let's not kid ourselves: elite sport is discriminatory. But not everyone can be a pilot either; certain skills are required to undertake specific tasks".

    Rodney Walker, chairman of UK Sport, which oversees sporting development in Britain, is more cautious. "Screening would only ever give an indication, albeit a potentially valuable one, as to a child's athletic promise," he says. And it should be society as a whole rather than sport that judges whether using genetic screening is appropriate or desirable.

    Andy Coghlan


 
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