ABSTRACT
The analysis of individual genes and the detection of specific changes responsible for human genetic disorders has been an integral part of medical genetics services for some three decades, since the recognition of deletions within the dystrophin gene as causing Duchenne muscular dystrophy. The karyotype can be seen as the first ‘genomic’ investigation, because the entire set of chromosomes is examined, if rather crudely. Multiplex ligation-dependent probe amplification is an application of the polymerase chain reaction (PCR) in which it is not the patient's DNA that is amplified by PCR but, instead, carefully designed probe sequences. Single-stranded sequences of DNA from across the genome are laid out in a structured array of microdots. The different types of mutation that may produce genetic disorders have already been mentioned briefly; many of the mechanisms were already known from studies on Drosophila and other experimental organisms and from work on much studied molecules such as human haemoglobin.
