On pages 184-185, Dr. Moalem considers AP Biology Big Idea 4
(Biological
systems interact, and these systems and their interactions posses complex
properties) by discussing the lamin A protein and its relation to
premature aging. He references the unit we previously studied and things Sam Rhine
mentioned when explaining about mutations that cause defective lamin A.
Firstly, explain both the function and structure of normal
lamin A and defective lamin A. Then relate the differences in these two
proteins to the possible types of mutations that can cause the differences.
Briefly explain when and how these mutations occur using your previous
background knowledge of DNA and DNA replication.
Secondly, relate the above information to the difference in
both severity and timing of Hutchinson-Gilford progeria and Werner syndrome
(mentioned on page 184). Compare and contrast the two diseases using outside
information. Be sure to include any similarities or differences in mutation
location, history of the disease, treatment, current and previous research,
statistics, and symptoms.
Lastly, explain why it is significant that the accelerated
aging is related to normal aging on the genetic level. Find an outside
experiment (not cited in the book) that uses this information to better
understand the ability to turn aging on and off. What are the implications of
this experiment? Is there any further research that can be done to expand the
understanding of human aging and how our knowledge of progeria can be used?
(Morgan Eisenstot – meisens4@students.d125.org)
The mutation that causes Hutchison-Gilford progeria syndrome is a point mutation on the 1st chromosome, section q, area 22. The gene that is disturbed is known as the LMNA gene, a gene that codes for lamin A. Lamin A is a structural protein used within every cell to support the nuclear membrane. Healthy lamin A has cytosine at position 1824, but a point mutation in the LMNA gene causes cytosine to be replaced with thymine in the defective protein. (http://ghr.nlm.nih.gov/gene/LMNA) This deformed lamin A is known as progerin and leads to a deformed nucleus, which lends itself to rapid degeneration.
ReplyDeleteWerner Syndrome is a similar disease, at least on the surface. Werner syndrome describes a late-onset, milder form of progeria that appears in adolescence and proves fatal by the late forties. The cause of Werner Syndrome is different than that of progeria: a mutation occurs on the WRN gene in chromosomal position 8p12 that affects the Werner protein. The Werner protein is a helicase that unzips DNA in the nucleus, thereby playing a vital role in DNA replication and transcription. A variety of mutations may wreak havoc in the WRN gene, mutations that lead to decreased stability of mRNA or truncation of the Werner protein itself. If the protein is disturbed by a mutation, it becomes less likely to adequately repair DNA, which leads to molecular degeneration associated with premature aging(http://ghr.nlm.nih.gov/gene/WRN)
A recent scientific study done by several professors at Columbia, entitled “The Mutant Form of Lamin A that Causes Hutchinson-Gilford Progeria Is a Biomarker of Cellular Aging in Human Skin” is a prime example of how knowledge of progeria will further our knowledge of the human aging process. The study involved taking skin samples from 97 unaffected subjects of varying age and comparing them to skin samples from progeria sufferers. The study concluded that progerin is a natural biomarker of human aging, and most of the progerin is stored in the papillary dermis of young skin. As a subject ages, however, the progerin penetrates deeper into the skin and is associated with “senescence,” or deterioration with age.
--Aidan Murphy, amurphy4@students.d125.org
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