Biology Reference
In-Depth Information
zebrafish is a remarkably useful model for studying development and
genetics (Driever and Fishman 1996). A major advantage of the zebrafish
is that the embryo is transparent, which means that subtle developmental
phenotypes can be studied in vivo. Additionally, comparative mapping
demonstrates that the human and zebrafish genomes have regions in com-
mon (Woods et al. 2000), and function of orthologous genes can often be
analyzed more effectively in zebrafish than in other species.
5. Genetic Counseling
The importance of imparting state-of-the-art scientific knowledge concern-
ing diseases to patients cannot be overemphasized. At the same time, this
information must be provided accurately and in a way that does not leave
the patient with unrealistic or false hopes for diagnosis or therapy. A genetic
counselor is trained to provide this information. Arnos and Oerlich
(Chapter 9) provide a clear and thoughtful discussion of the critical role of
the genetic counselor. Genetic counseling attempts to answer questions
concerning etiology (e.g., Why is our child hearing impaired?) and risk (e.g.,
What is the chance that we will have a hearing impaired child?). These ques-
tions may come from the parents of a child with hearing impairment, from
a hearing impaired individual who wants to have a child, or from a person
who has hearing-impaired relatives. As well as answering these questions,
the genetic counselor can provide information concerning the availability
of genetic diagnostic testing. A critical part of genetic counseling is making
sure that the patient understands the information being conveyed. It is
essential that there be no communication barriers, and genetic counseling
of hearing impaired individuals must be done in an appropriate manner
using visual material and/or a sign language interpreter.
The possibility that the hearing loss may be part of a syndrome must
be considered, and the genetic counselor again has the knowledge to inform
the patient or parents. For example, a child may have Jervell and Lange-
Nielsen syndrome, or Usher syndrome (Griffith and Friedman, Chapter 6),
and testing for these syndromes may be appropriate. In particular, bio-
tinidase deficiency can cause a form of genetic deafness that is preventable
if the deficiency is detected and treated. Thus, testing hearing impaired
infants for biotinidase deficiency in states where newborn screening for bio-
tinidase deficiency is not mandatory should be recommended.
6. Gene Therapy
Gene therapy is the term used to describe a method of treatment of a
human disorder in which a gene is transferred into the cells of the particu-
lar organ that is affected. A normal copy of the gene that is deleterious in
