MOSAIC MOMENTS

One of the questions that came to me today was “If my sibling has Down syndrome, will my child have Down syndrome?”

The answer is “more than likely not”.

Chromosomes are the units of genetic information that exist within every cell of the body. Twenty-three distinctive pairs, or 46 total chromosomes, are located within the nucleus (central structure) of each cell. When a baby is conceived by the combining of one sperm cell with one egg cell, the baby receives 23 chromosomes from each parent, for a total of 46 chromosomes. Sometimes, an accident in the production of a sperm or egg cell causes that cell to contain 24 chromosomes. This event is referred to as nondisjunction. When this defective cell is involved in the conception of a baby, that baby will have a total of 47 chromosomes.

Trisomy 21 Down syndrome is not inherited. This is just a beautiful fluke during cell division.  And,it is important to take into consideration that it is THIS particular sperm and THIS particular egg together that developed the extra chromosome.

Translocation Down syndrome can be inherited, but not always. So, if a sibling has translocation Down syndrome, the way I understand it is, if it is hereditary then a sibling or other relative could be a carrier of the gene.

I do know of some families who have a Aunt or cousin or some other relative who has Down syndrome and then they have a child with Down syndrome too. I find this very fascinating. However, the doctors remain that this is just a fluke.

Then, if a person has mosaic Down syndrome they have an increased chance (compared to one with T21) of have a child with 46 chromosomes instead of 47. It all depends upon where the affected cells are located in the body.

I hope that helps you understand a little bit more about the relative connection with Down syndrome. Feel free to leave comments and ask all the questions you have! If you don’t ask, you don’t know!

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