Detecting genes that influence complicated traits is a formidable task, he said, and current technology is limited.

Tests can now detect genes for more than a dozen diseases, and for factors that contribute to dozens more.

Therefore, we need to set up a realistic goal, say, to detect genes with effect size 0.5.

Tests have been developed that can detect altered genes.

Gene chips, which detect genes that are active, meaning they are being used to make a protein, have become essential tools.

In addition 4 of the 53 detected genes whose levels had previously been described as unchanged by axotomy also did not vary on the arrays.

They also made other technical innovations in the test that made it more reliable in detecting fetal genes.

The methods were compared in terms of their ability (or failure) to detect genes defined as having (truly) altered expression.

The new developments include very early sampling of foetal tissue to detect defective genes.

It is well suited to detecting particular genes whose expression varies between experiments.