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chromosome 3

Chromosome Deletions

Each person typically has a pair of number 3 chromosomes.  There are two segments in the chromosomes, one being the "p" arm, the other the "q" arm (see right diagram).  The karyotype name will specify which segment of the chromosome is affected.  A deletion in a chromosome means that a part or segment of one of the chromosomes is missing.  It can also be called a partial monosomy.  A monosomy means that there is the presence of only one chromosome instead of the typical pair.

If you see "del" in a karyotype name it means deletion.

Many of our children have what is called an intersititial deletion meaning "within" the chromosome. This would entail two breaks in the chromosome with a segment missing and the remaining segments joining up.

If a segment near the centromere is missing it is called a proximal deletion.

If a segment near the telomere is missing it is called a distal deletion. You may see a "tel" in the karyotype to describe this.

Sometimes there is only one break in the chromosome which is called a terminal deletion meaning that it goes to the end of the chromosome thus the terminology "ter" in the karyotype name (this does not mean the deletion is any worse than the others).

A very small deletion is called a microdeletion.