What is the outcome probability for live births in a 14/21 Robertsonian translocation?

In the context of a 14/21 Robertsonian translocation, understanding the outcome probabilities for live births requires an understanding of the genetic implications of such a translocation. A Robertsonian translocation involves two acrocentric chromosomes fusing near the centromere, resulting in the loss of the short arms and potential chromosomal imbalances in gametes.

When individuals with a Robertsonian translocation such as 14/21 conceive, they can produce gametes that may either maintain the translocation, be normal, or have duplications or deletions of genetic material. Specifically, for a parent carrying a 14/21 translocation, the child can inherit:

1. A balanced chromosome complement (normal or translocated) resulting in normal chromosome counts.

2. An unbalanced chromosome complement that can lead to Down syndrome, specifically if the child inherits the extra chromosome 21.

3. Non-viable conceptions due to imbalances arising from the translocation.

In terms of numerical probabilities, the literature suggests that for a couple where one partner carries a 14/21 Robertsonian translocation, approximately:

• One-third of conceptions may result in non-viable pregnancies (indicative of miscarriages).

• One-sixth may lead