Is Trisomy 13 inherited?
In most cases, trisomy 13 is not inherited. Trisomy 13 most often occurs because of a random mistake in the division of egg or sperm cells. However, trisomy 13 can be inherited if a parent has a rearrangement of chromosome material that involves chromosome 13. This rearrangement can also be called a “balanced translocation”. Humans generally have 46 chromosomes (23 pairs) in every cell in their body. We label them chromosome 1, chromosome 2, chromosome 3, etc. Humans generally have two copies of every chromosome, including chromosome 13. Sometimes bits of chromosomes can swap places. For example, the top of one chromosome 2 and the top of one chromosome 13 could switch places. The swap is called a translocation or a rearrangement. A person with that particular translocation would have a balanced translocation, because they aren’t missing any genetic information. That person’s children would have an increased chance to inherit a chromosome abnormality though, like partial trisomy 13. Analyzing a parent’s chromosomes can determine whether a parent has a balanced translocation. Balanced rearrangements are identified in about 1/1000 individuals, usually through the birth of a baby with an unbalanced chromosome condition.
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