Human digestive system digestive system is subject to a wide range of disorders many of which can be congenital. Mouth diseases can also be caused by pathogenic bacteria, viruses, fungi and as a side effect of some medications. Mouth diseases include tongue diseases and salivary gland diseases. A common gum disease in the mouth is gingivitis which is caused by bacteria in plaque. The most common viral infection of the mouth is gingivostomatitis caused by herpes simplex. A common fungal infection is candidiasis commonly known as "thrush" which affects the mucous membranes of the mouth. There are a number of esophageal diseases such
Human disease modifier gene mutant alleles, including those in BBS2, BBS6, and possibly in other loci and they identified a digenic mechanism of inheritance in what was previously considered to be a simple, Mendelian disorder. Genetic linkage analysis and association studies are widely used methods of identifying modifier loci. The advent of new genetic markers and automated genotyping methods have led to great diversity in applications of these studies. Common methodologies used to identify human disease modifier loci include linkage analysis in families, candidate association studies, and whole-genome association studies. In an example of a familial linkage study, genotyping and linkage analysis conducted in