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As you and the Congressman are probably aware, it is
possible for private citizens to send in a saliva
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sample and obtain a detailed sequencing of their DNA.
Humans and our diseases are very |
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complicated: the super-category of 'blood cancers' is
often divided into five categories:
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| /1/
Leukemias /2/ Hodgkin lymphomas /3/ non-Hodgkin
lymphomas /4/ Myelomas |
| /5/ Others, such as
myelodysplastic syndromes and myeloproliferative
neoplasms. |
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Humans at present are estimated to have about 25,000
genes that code for proteins like insulin |
| and hemoglobin, and another
25,000 genes that have other functions. It is common
to encounter |
| genes that control other
genes, and there are epigenetic factors like
methylization and histone |
| modifications that can also
silence genes. After sampling the world-wide genetics
grapevine it |
would seem reasonable to say:
|
| /1/ not all cases of leukemia
have a genetic basis – the percentage of leukemias
that do – even when |
| divided by type of leukemia –
is an area of vigorous debate. That means someone
could have a |
| condition somewhere on the
wide-ranging leukemia spectrum without any obvious DNA
problems. |
| /2/ there are currently over
160 genes associated with various named leukemia
syndromes. The |
| number of defined
mutations of those genes is in the thousands - and
growing. For example, the |
| CEBPA gene on
chromosome 19 in the q13.11 region is implicated in
several types of acute myeloid |
| leukemia: if one has one of
six mutations one group of leukemias results; if one
has any of several |
| dozen other mutations one of
a different group of leukemias usually results. Of
course, some |
| mutations cause no known
problems. |
| /3/ it is also the case that
one can have known genetic effects but not display
symptoms. It is poorly |
| understood why some genetic
configurations result in early onset (childhood)
leukemias and other |
| genetic configurations result
in late onset (older than age 50) leukemias. |
| |
| Were someone somewhere on
Planet Earth fearful that they had leukemia a
reasonable strategy |
| would be to search for a DNA
sequencing company that has a panel (a list of genes)
for leukemia. |
| Then the customer has to hope
that the panel includes all of the 160-odd genes – or
that the panel |
| at least has the gene
involved in the customer's condition. Alas, things are
more complicated than |
| that: the DNA sequencing
company has to have lists of mutations for each gene
so that the |
| company can report back that
the customer's sequence for each of the 50,000 genes
purports to be |
| normal or is implicated in
leukemia. The lists of genes and their syndromes as
well as the lists of |
| mutations of those genes
change over time so a DNA sequence analysis done in
2019 might have |
| different results than one
done months earlier. |
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