Medknow Publications and Staff Society of Seth GS Medical College and KEM Hospital, Mumbai, India
Abstract
"Phenotype" is the visible or quantifiable effect of the expression of
a gene, whereas the specific genetic constitution responsible for a
phenotype is called "genotype". It was hoped that phenotype could be
accurately predicted if the genotype could be characterized. But, the
relationship between the genotype and phenotype is not straightforward.
Similar genetic lesions can have entirely different phenotypes. In
recent years, there has been tremendous progress in the understanding
of the genetic basis of diseases. The extent to which it will be
possible to relate findings at the DNA level to the clinical phenotype
is difficult to delineate on many occasions. The elucidation of
mechanisms underlying genotype-phenotype discrepancies is important as
it will influence the use of DNA-based tests in the diagnosis, therapy
and counseling of individuals affected with genetic disorders. This
issue is pertinent to almost every aspect of medical practice and
research in this post-genome era. In this article, we have tried to
summarize those factors which are responsible for varied manifestations
of lesion(s) in a single gene