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  • Subject: [iris-photos] Re: SCARLET BUTTERFLY
  • From: "nmogens" neilm@charter.net
  • Date: Thu, 24 Jul 2003 00:42:21 -0000

--- In iris-photos@yahoogroups.com, "donald" <donald@e...> wrote:
"Karotype analysis is not the same as chromosome counting, is it?  
Isn't it more akin to DNA testing in that it identifies a chromosome 
as being a marker for a specific species?  Not as specific as DNA 
testing, but still enough to identify the probably ancestral source
(s) of the chromosomes. --Donald Eaves"

During some post-graduate continuing education I did a "one-hour" 
Readings and Conference stint in cytogenetics.  The prof. had me 
learn how to make and stain slides where chromosomes could be 
counted.  I did serial sections of root tips of one of my own 
varieties, SWEET HOOGIE, as it was recorded in my stud book as being 
from Blue Shimmer X (Sun Lakes x I. hoogiana).  It was expected to 
have the eleven chromosomes of the regelia and three sets of twelve 
from the TB ancestors.

I found making the slides extraorinarily laborious.  It is not done 
quickly!  I spent nearly an entire day just going through the 
procedure, clumsily, I admit, as this was my first and only time to 
engage in such a project.  Additionally I had spent quite a few hours 
prior to the exercise reading to learn the process.  Only then, the 
slides prepared and dry, was I able to begin to try to count and 
identify marker chromosomes.

Thanks to the karyotypes (diagrams of the shapes of the chromosomes 
in a set) published in *Garden Irises*, the predecessor of *The World 
of Irises*, I was able to find and identify the long metacentric 
chromosomes (ones where the waist-band is in the middle) 
characteristic both of regelia and tall bearded clones.  I found the 
two chromosomes remarkable different, the regelia one being 
significantly longer than the TB, if I am remembering correctly.  I 
did this a mere forty years ago, so the memory is "fresh," if I may 
be a bit tongue in cheek.

Some of the other significant chromosomes were those that 
were "acrocentric" with satellites (waist band near one end, and 
having a tag-along even further out, just barely attached)--again my 
memory may not be perfectly accurate.  Identifying the morphology 
(form) of the significant chromosomes was far easier than counting 

The net effect of the experience was (1) the parentage was probable, 
and (2) I had enormous respect for those people who do this sort of 
work on a serious basis.  I found out why chromosome counts vary--
chromosomes are very hard to focus on and see.  It would be very easy 
to miss one that could have been seen, or a small chromosome may be 
partially or fully obscurred by one of the larger ones and not be 
visible enough to note.  To try to photograph the sets would be even 
more difficult--the optical field on the slide is significantly 
greater than the depth of field offered by the microscope.  It would 
be like trying to read a dictionary with a magnifying glass, then 
turn and try to see the TV through the same magnifying glass at the 
same distance from ones face.  All is lost in a blur. 

I just sat with a sketch pad and worked the focus up and down with 
the fine-tuning adjustment and tried to draw what I thought I saw.  
The results may have been grounded more in my expectations and 
imagination than in what came through the microscope into my eye.

To say the least, an iris that is supposedly (aril x TB) X TB *can* 
be identified as either "is" or "is not" with this procedure, both by 
the number of chromosomes and by the shapes (morphology) of the 
chromosomes (the karyotype).  In any event, what an experienced 
person sees when looking at the plant tells one just about as much at 
vastly lower cost and with a great deal less time.

Neil Mogensen  z 7 western NC

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