Visual communication aid: Reciprocal chromosome translocations

There are two communication aids available to view and download (.pdf) for this topic:

• Reciprocal chromosome translocations
• Reciprocal chromosome translocations: pregnancy outcomes

Double-sided printing in colour is recommended (but not required). All content is also included below in an accessible format.

More information about these and other VCAs is available in this article.

We all have over 20,000 genes, which provide instructions for how our body works. Genes are made of DNA. Our genes are packaged into structures called chromosomes. ​

Individuals usually have 46 chromosomes in each cell in their body. These are arranged into 23 pairs. ​
Sometimes, when cells divide to form eggs or sperm, or during early development of a baby, chromosomes may break and repair themselves incorrectly. ​

In some cases, segments of two chromosomes may break off and swap places. This means there is still the correct amount of genetic information, just in a slightly different arrangement.​

This is known as a balanced reciprocal translocation (figure 1).

Generally, balanced reciprocal translocations do not affect an individual’s health as no genes have been lost or gained.
If either parent of a pregnancy carries a balanced reciprocal translocation, this can affect the outcome of the pregnancy.

Figure 1: Balanced reciprocal chromosome translocation

When either parent of a pregnancy carries a balanced reciprocal translocation, there are several possible outcomes (figure 2):​

1. The pregnancy does not carry a translocation.​
2. The pregnancy carries the same balanced translocation as their parent. In general, this has no effect on the pregnancy or health of the child.​
3. The pregnancy inherits an unbalanced form of the translocation. This means the pregnancy has inherited an extra piece of one chromosome or is missing a piece of one chromosome. This may lead to pregnancy loss or having a child with a chromosome condition.

Potential outcomes of a pregnancy may differ depending on the size and location of the chromosome translocation. Some outcomes may therefore be more likely than others.

Figure 2: Potential pregnancy outcomes when one parent carries a balanced reciprocal chromosome translocation
(View larger image)

• Chromosomes: Packages of DNA which are found in our cells​.
• Balanced translocation: The term used when two or more chromosomes have been rearranged, but no DNA is lost or gained​.
• Unbalanced translocation: The term used when a chromosome rearrangement has caused DNA to be lost or gained.
• Trisomy: Having an extra copy of a chromosome​.
• Monosomy: Having just one copy of a chromosome instead of two.

For patients

• Unique: Balanced Translocations
• Unique: Unbalanced Translocations