Genetics is fundamental to an understanding of differences
between individuals and between populations. Common minor
differences are found within what is generally accepted as the
normal range of variation, while relatively unusual but more major
differences may be appropriately considered under the heading of
pathology. Both major and minor differences occur in terms of
structure, function or susceptibility to disease. This submission
contains examples of such differences and their exploitation or
analysis, most of which fall within the general field of dentistry.A number of observations of inherited dental abnormalities in
man and experimental animals are included. These indicate that
there can be compensatory interaction between neighbouring tooth
germs during development. Based on this interaction, a model to
account for differential evolutionary reduction of tooth size is
proposed. Studies of regional differentiation in the mouse vertebral
column are described, the vertebral column being a series of
homologous structures divided into morphological classes in the same
way as heterodont dentitions. The effects of a number of inherited
disorders of the axial skeleton indicate that vertebral class
boundaries in the mouse are established at a very early stage, even
before somite formation. The use of dental morphology for population
discrimination is discussed in relation to studies of the genetics of
dental morphological variation, and a population comparison in which
the discriminating power of dental morphology was tested against that
provided by known genetic variants.Studies of inherited iron-deficiency anaemia in the mouse are
described. They show that the disorder is associated with thinner
lingual epithelium than normal and possibly with increased susceptibility to oral candidosis. Different strains of Candida produced
different levels of oral colonisation and infection in normal mice,
suggesting that susceptibility to candidosis may be related to
variation in the microorganism as well as the host. A human family
study of Paget's disease of bone is reported. The results are
consistent with the hypothesis that Paget's disease is caused by a
common virus, with genetic variation for susceptibility to the
disease. Also in man, a comparison between carriers of X-linked
hypohidrotic ectodermal dysplasia (in whom manifestations of the
disease may be limited to minimal hypodontia) and females with
hypodontia for other reasons indicates that carriers may be
distinguished from among female hypodontia cases in general by means
of a reduced sweat pore count.In the past, various genetic principles have been misapplied in
dentistry. Two critiques of such misapplications are included,
together with contributions to a review of current dental research,
undergraduate and postgraduate dental texts, and a major new medical
genetics text
