As we talk to people, we realize that this is a topic most people have no clue of. And why should they? Unless you're in the research field working on chromosomes, or unless you have been directly hit by 2 translocated chromosomes at some point in your life, you wouldn't know what they are and the impact this could carry.
What is a chromosome translocation? It is the re-arrangement of parts between different chromosomes. There are 2 types of translocations:
Reciprocal (the kinds DH has) and Robertsonian.
Further, the translocations can be Balanced (where the total chromosomal material is not impacted) and Unbalanced (where the exchange of chromosomal material is not equal)
DH has a Reciprocal Balanced Translocation on his 11th and 22nd chromosomes. This means a part of chromosome 11 broke and got attached to chromosome 22. An equal portion of 22 broke and got attached to 11. This means DH's chromosomal material is complete - he is not missing any genetic information, neither does he have any extra.
Here is an image
We carry 2 sets of chromosomes - one set from Mom and one from Dad. When a sperm or egg is made, it comprises of 1 set of chromosomes, and fertilization is what completes the 2 sets.
In the case of a balanced translocation chromosome carrier, there are chances that his / her gamete (sperm or egg) COULD be balanced or normal, or could be unbalanced. Here is an image which shows the probability:
This is the normal / standard probability. However, individual numbers or rates would vary. For example, in our case, we seem to have only 1 in 10 embryos turn out normal / balanced. So our rates don't appear to be the 33% that shows up in this diagram. In our case we fall in the low 10% category.
(Please Note: This image shows a translocation on both arms of the chromosome. DH's is single arm - so his percentages may differ - I'm still looking for an appropriate image to post here)
.16% of the world's population (1 in 625 people) carries a translocation. In most cases translocations go undetected until this person experiences infertility / multiple miscarriages, or has a baby with birth defects which are chromosomal in nature and traced back to parental karyotypes.
If a couple gets pregnant with an unbalanced embryo, the woman will most likely miscarry the baby. In some cases, pregnancies do carry on to full term, and the couple may have a baby which is severely disabled in multiple ways.
The way we can bypass this is by subjecting our embryos to PGD and selecting only the normal / balanced ones for transfer. Some studies say embryos formed from gametes of a balanced translocation carrier could be more pre-disposed to aneuploidy. We don't know that for sure yet.
It's been a fascinating and at the same time extremely daunting and scary topic to research. Today I found an article which talks about the EXACT same translocation that my DH has, except in this case it is the mother who has the translocation. So her karyotype begins with 46 XX and DH's begins with 46XY. The rest of the karyotype is exactly the same. This poor woman had a baby with an unbalanced translocation (she did not know about her translocation till the baby was born with special needs) and needless to say, her life and world have been turned upside down since then. I got goosebumps reading the article. Here is it for those that are interested:
The purpose of this post is to bring some awareness to our reality. We talk this language EVERYDAY, and are scared out of our wits. Sometimes we think that most REs don't really know this subject that well, and we have often heard our REs admit they don't. They refer to their knowledge as something that is really the embryologist's knowledge. We have now started emailing doctors and scientists in Japan and China etc to get some more insights.
At the end of this - I am going to demand an honorary PhD in the topic! :-)