RE: Stable Reciprocal Translocation Blood Test

["Carlisle, Sara" <carlisles@aecl.ca>]

Bruce:

A stable reciprocal translocation blood test looks at the frequency of
"reciprocal translocations" in circulating white blood cells.  In cells,
the genetic material, DNA, is packaged into sub-units called
chromosomes. When DNA is damaged there can be rearrangement of these
sub-units, leading to events collectively known as chromosomal
aberrations. Certain classes of chromosomal aberrations (i.e. reciprocal
translocations) are stable and can be used to determine lifetime
cumulative radiation exposures. Other chromosomal aberrations, such as
dicentric chromosomes, can be used to assess recent exposures - these
aberrations are not stably inherited, since they affect partitioning of
genetic material between daughter cells during cell division.
Chromosomal aberrations are the end-points traditionally measured in
biological dosimetry and have, for example, been used extensively in
studies of the Japanese Atomic Bomb survivors. 

To measure chromosomal aberrations, white blood cells are isolated from
a blood sample, stimulated to divide (with PHA - phytohaemagglutanin)
and then treated with a chemical (colcemid) to stop cell division at a
point where individual chromosomes can be seen (metaphase).  The
chromosomes are stained with dyes, and examined by a cytogeneticist who
looks for abnormal chromosomes. Recent advances in molecular biology
allow specific chromosome pairs to be stained with dyes that
differentiate them from the remaining chromosomes (chromosome painting),
which makes detection of reciprocal translocations much easier than
traditional non-specific staining techniques, which relied on
recognition of changes in complex banding patterns on the chromosomes
for detection of chromosomal abnormalities - a very tedious exercise
that required a very experienced cytogeneticist.

Hope this helps. I'm not actually doing these assays myself, but staff
here at AECL are doing research involving reciprocal translocation
assays on blood samples.  If my explanation is too full of molecular
biological jargon, let me know and I'll give it another shot.

Sara Carlisle
Radiation Biology and Health Physics Branch
Chalk River Laboratories

phone (613) 584-8811 extn. 3667
email carlisles@aecl.ca

> ----------
> From: 	Pickett, Bruce D[SMTP:Bruce.Pickett@PSS.Boeing.com]
> Sent: 	March 2, 1998 10:42 AM
> To: 	Multiple recipients of list
> Subject: 	Stable Reciprocal Translocation Blood Test
> 
> Does anyone know what a "stable reciprocal translocation blood test"
> is?
> Please provide any details which you can think of in your response.
> 
> Bruce Pickett
> bruce.d.pickett@boeing.com
>