The idea behind Jeans for Genes day - swap school uniform for a pair of jeans and pay a pound towards research into genetic disorders - is simple.

This casual approach to the complicated business of genetics has already proved successful. Last year the appeal, organised by Great Ormond Street Hospital and three other specialist charities, raised Pounds 800,000.

But it’s not just about fun with puns. The science of this fast- evolving area is complicated, and the serious side is that there are about 4,000 known genetic disorders, including cystic fibrosis, muscular dystrophy and haemophilia.

The headlines that made a celebrity of Dolly the cloned sheep or warn darkly about the dangers of tinkering with our DNA, hide a multitude of ethical and scientific concerns. The teaching packs accompanying this year’s appeal aim to inform primary and secondary pupils of them.

The two free packs of materials, which include worksheets, teacher’s notes, and case studies have been produced by the Progress Educational Trust, a charity which grew out of the research body that helped steer the Human Fertilisation and Embryology Bill through Parliament.

“There was a high demand for teaching materials to go along with the day, ” says co-author Juliet Tizzard. “Genetics is something that is changing very quickly, so it is difficult for biology teachers, let alone anyone else, to keep up with what is going on and to decide what is suitable for teaching their students. ”

The basics of genetics - inherited characteristics such as eye and hair colour - can easily be understood by small children. One way of helping pupils make the imaginative leap from the obvious to the microscopic is by using a cassette tape as an analogy where genes are the recording, the DNA is the tape and the chromosome is the cassette.

This is a useful image in helping children visualise the make up of the human body. But it is still a difficult concept to grasp, and overall the materials for primary use would stretch any teacher without a science degree.

The case studies bring home the chronic and debilitating effects of some genetic abnormalities but lapse into technicalities. How many seven-year-olds need to know that “Mucopolysaccharide Diseases . . . inherited in autosomal recessive fashion”? Or - as the teaching notes suggest - could even read it?

Jackie Hardie, deputy head of Latymer school in London and a former science adviser, who uses the jigsaw puzzles analogy in her teaching, thought the tape comparison “a nice idea”.

She acknowledges that genetics is a difficult subject to teach (“even A-level kids don’t appreciate the scale of things”) but wondered whether even the most high-flying GCSE students could digest the more detailed explanations: “They would need to sit down with a really good teacher to get something out of this.”

The primary pack starts with a worksheet asking pupils to fill in a family tree of the three generations featured in the accompanying photograph.

But replicating the exercise in class can “have unexpected repercussions”, the teacher’s notes warn, and could be as hurtful as using pupils’ height or weight to illustrate biological variation. Using the Royal Family as an example, as the notes suggest, might not be a good idea either, given recent events.

“Throughout the pack, students are prompted to consider some of the social and ethical implications of the new genetics,” the authors say. “It is only when something becomes real to them that they learn - and remember - scientific facts.”

But most children would relate better to the suffering of their peers if these case studies were written in the first person, focusing on everyday experience with appropriate explanation, rather than the social services adopt-a-child style.

The secondary pack bears the hallmarks of a scientific journal. It goes into great detail, but the graphics and layout don’t give easy access to the densely written text. And the accompanying Progress Guide to Genetics, written by Marcus Pembrey, professor of paediatric genetics at the Institute of Child Health, is a pamphlet best suited to A-level students.

Perhaps computer-generated models are the best way to illustrate the intricacies of DNA. When the budget doesn’t run to a CD-Rom you’re always going to struggle to explain it. But why no mention of, say, DNA profiling (to eliminate suspects or establish paternity), as an example younger pupils will have heard of and a way of introducing them to a difficult subject?

Jeans for genes is an inspired idea. But compared with the cleverly targeted fundraising scheme, the teaching materials are pitched way over most pupils’ heads.

Further details from Jeans for Genes Day, Great Ormond Street Hospital. Tel 0171 916 5676