What is a Chromosome 3 Deletion?
Chromosomes are found in nearly every cell of your body in the nucleus of each cell. The cells in your body have 23 pairs of chromosomes in each cell which makes a total of 46 chromosomes each. Your red blood cells do not have a nucleus and therefore do not have chromosomes in them. The male sperm cells and female egg cells contain only 23 chromosomes each because when they join they normally give one chromosome each to the developing embryo. The chromosomes contain our DNA which makes us who we are.
This picture shows a cell with the nucleus and the chromsomes contained in it. The picture to the right shows that the middle of the chromosome is referred to as the centromere and the ends of the chromosome are referred to as the telomere. The shorter portion of the chromosome above the centromere is called the "p" arm and the longer portion below the centromere is called the "q" arm of the chromosome. You will usually see "p" or "q" in the karyotype name.
A deletion in a chromosome means that a part or segment of the chromosome is missing (please see the black and white segments in the pictures of pairs of chromosomes below.) It can also be called a partial monosomy (monosomy means that the person has one less chromosome). 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.
| Karyotype and G-Banding below shown by bright field G-banding of chromosomes. Click on the picture below to view the 23 sets of chromosomes in greater detail. Notice chromosome 3's black and white bands or segments. The picture to the right is chromosome 3 in greater detail. You can determine which bands are missing in each deletion. | |
| Normal Human Karyotypes: | |
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| Male | Female |
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| Website's for chromosomal anomalies and rare disorders
Chromosome Deletion Outreach (CDO) Unique Rare Chromosome Disorder Support Group Please see Unique's "Little Yellow Book" for in depth information on rare chromosome disorders The National Human Genome Research Institutes Glossary of Genetic Terms The National Organization for Rare Disorders (NORD) NORD |
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If you would like your family member added to the site or to get contact information for any family, please contact chromosome3@cox.net
We would like to thank the following companies, institutions, university's and websites for the use of their pictures and information.
The University of Washington, Department of Pathology. For more information click www.pathology.washington.edu
The National Human Genome Research Institute.www.genome.gov
