GUIDELINES for the use of DNA in the classroom have been called for after a report that medical students have been testing their own genes for inherited diseases such as cystic fibrosis, Alzheimer's disease and heart problems. Two years later, this rate was reduced to 12.5 per cent.Under Mrs Thatcher, the higher rate was abolished in 1979 and a unified rate of 15 per cent introduced. Widget-makers can offset tax paid on goods (inputs) they buy against tax on their own goods.Ever since it was introduced in Britain in 1973, at a standard rate of 10 per cent, VAT has become increasingly complicated with some products exempted or zero-rated, and different rates levied on various groups of goods and services.In July 1974, the standard rate was reduced to 8 per cent, and four months later a higher rate - 25 per cent - was introduced on petrol. The tax is based on the difference between the value of the output over the value of the "inputs" used to produce that output. A widget-maker sells his widget for pounds 10, of which pounds 8 is goods or inputs used to make it, and pounds 2 is profit. If VAT is 10 per cent, the product is sold for pounds 11, with pounds 1 being the tax paid by the buyer.

IT'S cumbersome and complicated - but Value Added Tax is a sure- fire way of raising revenue, particularly for Chancellors who don't want to be seen to be adding to voters' direct tax burden It works like this. Mr Hughes said: "The bell industry is about to be taxed more heavily than in its history, but it's a decision taken by a few officials without a change of law in either Europe or Westminster."Mr Hughes has enlisted the support of Tory backbencher Sir Patrick Cormack, who haswritten to ministers. John Taylor's bell foundry in Loughborough has lobbied its MP, the Health Secretary, Stephen Dorrell.Meanwhile, the Council for the Care of Churches is stepping up its efforts to have all work on historic buildings zero-rated.. Its credits include Great Paul in St Paul's Cathedral (16 tons), Great George at Liverpool Cathedral (14 tons) and Great Peter in York Minster (10 tons).The managing director, Alan Berry, said: "Taxes collected from bell work would only be about pounds 300,000 over the next few years, but many projects must be at risk."At Whitechapel, usually keen rivals, there is total agreeement. To suddenly have a few thousand pounds added for no good reason sets you back dreadfully."The bell foundries admit there could be a short-term boom if churches scramble to order in the next few weeks, but longer-term job prospects could suffer.At John Taylor Bell Founders, in Loughborough, where bells have been made since the 13th century, the mood is gloomy. "Raising money for bells is a specialised business and it was a measured risk to launch the appeal We wanted people to hear these bells 100 years from now. The church is not rich, with its contribution quota to the diocese already up by a quarter.

The parish council gave pounds 5,000 but most fund-raising took place outside the village, including donations from bell-ringing trusts."The school and community hall always need cash and it wasn't felt right to raise bell money here," said the Reverend Stephen Little, the rector. "It's touch-and-go whether we can order within the next few weeks," lamented Jennifer Cross, of the appeal trust.The Church of St James the Great, at Harvington, near Evesham in Worcestershire, has raised pounds 11,000 towards the pounds 30,000 estimate for rehanging its bells. This has caused frenzied activity in the shires, prompting fears that some appeals may over-commit themselves in the dash to save cash.Most churches, like St Peter's at Thornton, will not meet the deadline. Others, like St Mary's at Sampford Spiney, near Tavistock in Devon, which is close to its appeal target of pounds 35,000, may be better-placed.