ABSTRACT
Genetics is traditionally defined as the science of biologic
variation, and has been a scientific discipline for over 100
years. Human genetics makes up a large part of the field of
genetics, but the principal laws of genetics are universal, and
apply equally to all species, including humans. Mendel’s
studies in the 19th century were originally felt to have no
relevance to humans, and it is only in retrospect that their
importance can be seen. Many of the principles of genetics
were discovered through the study of smaller organisms, such
as bacteria, yeast, and fruit flies. The basic genetic mechan-
isms of cell division, development, and differentiation
happen in the same way in widely divergent species. There-
fore it is impossible to look at human genetics in isolation,
and there are large amounts of information from lower
species which have bearing on human disorders. The study of
the genetics of small organisms has had a profound impact
on our understanding of human development, and of how
human diseases develop. It is likely that such basic science
will continue to contribute significantly to the understanding
of human genetic disease. This chapter will attempt to outline
the basic elements of genetics, describe the types of genetic
tests now available to help in neonatal diagnosis, and give an
approach to the diagnosis of congenital abnormalities.
