Linkage Analysis

Linkage analysis is the technique typically used to determine the genetic location of a disease gene when there are no other 'signposts' available (no cytogenetic abnormality, co-inherited disorders, good candidate genes, or known protein product). The goal of linkage analysis is to identify a piece of DNA of known location that is inherited by all family members affected by the disorder being studied, and is not inherited by any of the unaffected family members. This piece of DNA is said to be 'co-inherited' or to 'co-segregate' with the disease phenotype. Once this piece of DNA is found, one knows that the disease gene must lie somewhere close by. Determining the location of the disease gene is the first step toward identifying the gene itself. (more from Engle Lab.)
Some Web links that can be interesting:

• Cookbook Linkage Analysis course outline from Alejandro A. Schäffer from NCBI.
• NIH's BIMAS linkage analysis page, including info on troubleshooting LINKAGE software error messages.
• Dave Curtis's lecture notes in genetic linkage and association analysis.
• List of linkage analysis and gentic software at Rockefeller University.
• Mirror on our FTP site of some packages for linkage analysis and mapping.
  

Genotyping

Genotyping is characterisation of an organism in terms of its heritable material, DNA. We use microsatellite markers to characterise an organism. Microsatellites, also called short tandem repeat sequences (STRs) are regions of DNA where the base sequence is repeated. The most common repeats in humans are dinucleotide repeats but tri- and tetranucleotide repeats are common. The repeating pattern can be up to 7 bases in length. (read the Genotyping Faq at AGRF)

---