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Thursday, May 25, 2017
Inherited Disorders and Birth Defects
Balanced translocation 14;18
My friend just found out that like her father she is a carrier for a balanced translocation between chromosomes 14 & 18 with the break points at q22. What implications does this have for her or her future ability to have children?
A balanced translocation occurs when two pieces of chromosomes break off and switch places with each other. If all the chromosomal material is present, just rearranged – that is, switched places (translocated) - this person should have no health problems since all the chromosomal material needed is present and functioning properly. This is called a balanced translocation. There is no way to tell whether or not a person has one of these rearrangements unless you look at his or her blood to examine the chromosomes - such as the case for your friend.
An unbalanced translocation is when some of the chromosomal material that was switched is lost or duplicated when the chromosomes broke and the switch took place – then there is extra and / or missing information that can lead to birth defects and cognitive problems such as mental retardation.
When a person with a balanced chromosomal rearrangement forms eggs or sperm, sometimes it leads to an unbalanced translocation at conception. The specific types of problems or birth defects would depend on what genetic material was lost or duplicated in the chromosomes that are translocated and what specific genes are located at these sites. While most pregnancies that have an unbalanced chromosomal rearrangement are miscarried, of those that make it to term - the abnormalities seen can range from mild to severe. If the abnormalities are severe, there is a greater chance that the child may die in infancy or early childhood. Life span is usually shortened in children with chromosome abnormalities, but not always. Mental retardation is almost always a part of the picture for children with chromosome abnormalities. In some unbalanced rearrangements (translocations) it is not possible to predict what abnormalities to expect or how severe they may be.
If she has not already done so, I would recommend that your friend speak to the genetic counselor or a geneticist to discuss the specific chromosomal translocation that she has. She can locate a genetics center near her at the National Society of Genetic Counselors’ Resource Center website below.
Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University