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syndromes of familial cancer have been reported in the medical
literature. They are academically interesting but usually rare.
The majority are inherited as autosomal dominant traits. Some of
these syndromes are associated with DNA repair abnormalities.
They are autosomal recessives. Examples are xeroderma pigmentosum,
Fanconi anaemia, ataxia telangiectaxia.
The genes responsible for the dominant
inherited cancer syndromes are usually tumour suppressor genes.
Tumour suppressor genes usually show three main characteristics:
1. germline mutation that affect one
allele generally causes a loss of function.
2. tumour also show loss of second allele
as a result of somatic mutation.
3. the normal function of the gene is to
suppress unrestrained cellular growth or to promote
differentiation.
So far the following genes have been
discovered and studied. These are RB, p53, NF1, ret, the HNPCC
mismatch repair genes, BRCA1, and BRCA2.
1. RB is a retinoblastoma gene. In a
pedigree analysis, a loss of function germline mutation occurs in
one allele of the RB gene in chromosome 13. Sporadic
retinoblastoma usually unilateral, is due to somatic mutation in
both alleles of the RB gene without any germline predisposition.
2. p53 gene is on chromosome 17p. This
gene is frequently altered in solid tumours. Mutations in p53 are
found in nearly half of human tumours.Germline mutations in p53
have dramatic consequences resulting in aphenotype known as Li-Fraumeni
syndrome where affected individuals may develop a variety of
sarcomas, brain tumours and leukaemia.
continue part 2
If you have questions related to this article you may e-mail me
at doctor@soontongkiong.com quoting the contents of the article.
About the author
DR SOON is a medical practitioner. He holds four degrees. MBBS
(University of Malaya), MBA (University of East Asia), LLB (Hons)
(University of Wolverhampton), Master of Medicine (Edith Cowan
University
:
Dr SOON is the owner of AskMyVisitor.com and MyScriptDoctor.com
where you can find the most up-to-date advice and information
on
many medical, health and lifestyle topics.
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