Hot answers tagged cytogenetics
Those are the break points of the inversion. So chromosome 4 was cut at p13 and q22 and the fragment was reinserted in the reverse direction, giving a pericentric inversion.
You have made an incorrect assumption-- that all the genes on both chromosomes necessarily remain intact. It's possible that they do, and the the translocation is harmless. But the transition point could be within a gene. This would usually lead to that copy of the gene becoming inactive, which can cause diseases just like any other loss-of-function ...
In the Down syndrom typically, the translocation does not induce (usually; see later) any disease. We call someone carrying the translocation a "balanced carrier". The problem arises after, at the moment of segregation. When balanced carriers reproduce Consider someone who has a translocation as you showed. You showed only one chromosome of each types ...
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