A particular haplotype defined by probes XV2c, KM19, and CS.7 at the D7S23 locus was found on 90% of chromosomes which carry cystic fibrosis (CF), but on only 11% of normal chromosomes in a UK sample of CF carriers. We show how such data can be used to calculate carrier risks for people with and without a family history of CF, and give examples of clinical applications. For parents or sibs of dead CF patients, phase and genotypes can often be assigned with only 1 to 2% error. However, this method is not suitable for prenatal testing where there is no history of CF; for couples with no family history, no fetus can be shown to be at more than 2% risk of being affected.

Adult↗

PubMedDate not supplied

Optimizing PCR conditions for HLA class II SSO typing.

The polymerase chain reaction (PCR) has made the technique of sequence-specific oligonucleotide (SSO) typing fast, accurate and very sensitive. These combined techniques are an ideal tool for analysing the complex patterns of polymorphism seen throughout the HLA complex. The success of the technique relies heavily on accurate and specific amplification of the DNA under study. This paper considers the principles behind the PCR amplification technique and discusses the factors which lead to optimal amplification. Primer design is discussed and a variety of sources of target DNA considered. Precautions designed to prevent contamination are discussed. Reaction components are considered both in isolation and as part of the complete reaction. Finally, a complete PCR protocol is suggested. The paper is illustrated with examples of HLA class II amplification.

DNA↗