translocations

P.L.Pearson P.L.PEARSON at med.ruu.nl
Tue Jun 11 08:09:22 EST 1996


Dear Tim, Ignore the posting in reply to your question on the genetic risks
of a new apparently balanced translocation in which it was stated that
there was no increased risk. That is just NOT true. For a de novo
"balanced" translocation there is a risk of congenital abnormalities
somewhere between 5% and 10%. The reason for that is that the translocation
may not be entirely balanced and may have gained or lost some genetic
material below the resolving power of the light microscope. Another
possibility is that the breakpoint could have gone right through a coding
sequence which would almost certainly inactivate the gene concerned. The
only way you can be reasonably certain that everything is ok if there is at
least one normal, healthy being carrying an identical translocation and by
identical I mean identical by inheritance (descent) and not just that the
breakpoints are in the same location as other known balanced
translocations. I agree with the last posting which stated that the advise
you received was dangerous.

        Peter Pearson,
        Dept Human Genetics, Utrecht





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