Question:

Our grandson is missing the 7th chromosome. There is a huge question as to weather the little guy is in fact my son`s child. If our son is tested and has all his chromosomes, then does that mean he`s not the father?

Answer:

The answer to your question is no – it would be very unusual for your grandson to have inherited a chromosome 7 that is missing a part of it. From your description, most likely your grandson is missing a piece of one of his chromosome # 7 (this is called a deletion). I do not know of any babies being born that are missing an entire chromosome 7 – those pregnancies would always miscarry. Occasionally, when cells divide they do not divide correctly and a piece of a chromosome can break off and be lost. These babies can have growth problems, birth defects and cognitive problems such as learning disabilities or mental retardation.

We would expect that the parents of a child with a chromosome deletion would have normal chromosomes (unless the parent has similar problems as the child). If there is a concern about who the father is – your son should have paternity testing done. The laboratory would look at more than just chromosome # 7, but they look at several different genes throughout all of the chromosomes (your son’s DNA) to see how alike or different it is from your grandson’s DNA.

For more information:

Go to the Inherited Disorders and Birth Defects health topic.