and Molecular Genetics III:
of Molecular Defects
November 16 (Friday), 2001
Required Reading: Principles
of Medical Genetics
Gelerhter TD, Collins FS, Ginsburg D
Williams and Wilkins
- You will be responsible for learning
about the molecular basis for disease processes through understanding
the examples of hemophilia as presented in your textbook. The basic
concepts that are important to know are nicely illustrated in the
figures presented in the textbook and you should be sure to understand
the general concepts illustrated in each of the figures.
- For hemophilia you should understand
the basic concepts of the disease process especially as related
- What kinds of mutations occur? How do they occur? Understand the
wide variety of different types of mutations that have been described
in Hemophilia A and the potential mechanisms underlying the mutations
especially for any novel mechanisms of mutation (eg. the
recurrent inversion, mutational hot spots) that are discussed in
- Inheritance pattern
How are Hemophilia type A and B inherited? Can both women and men
be affected? Why or why not? Understand that although most female
carriers of hemophilia A are asymptomatic that some female may exhibit
symptoms and understand why this may occur. Why are most female
Why are there different degrees of severity in hemophilia? How do
the levels of severity of disease correlate with the amount of circulating
Factor 8 levels. What are the basic molecular mechanisms underlying
hemophilia A and B?
- Molecular diagnosis as discussed
in the textbook. Understand
how cloning of the gene involved in this condition has enabled accurate
prenatal diagnosis by direct mutational analysis or linkage analysis
- Although you will need to know the clotting
cascade during your medical school career and will need to memorize
and regurgitate the information for other classes, you do not
need to memorize it for this class.... Really!
- Understand how cloning of the gene involved
has also the way for the development of recombinant factor used
for treatment and is also paving the way for development of gene
transfer applications. Consider how you might design gene therapy
for hemophilia. What levels of circulating Factor 8 would you need
to achieve? Where might you want to express the gene? (You will
have a gene therapy lecture later on in this course).
- Understand that defects at different
points in the clotting cascade may cause different bleeding disorders
and be familiar with Hemophilia B.
- Understand that gene expression of the
Factor IX gene and the resulting clinical phenotype may change during
different times of life and know one mechanism why this might happen.
- Understand why in both Hemophilia A
and B that 1/3 of all mutations are thought to arise de novo (Haldane).