… and what is it good for?

This is a pretty controversial issue, so you’ve probably already heard the term, but what does it really mean?

Genetic Diagnosis is a very generic term. Here, detecting Single Nucleotide Polymorphisms (SNPs)- single changes in the sequence of DNA- is what is veing investigated.

Preimplantation refers to our development. When a females egg is fertilized by a sperm, it takes several days before it reaches the uterus. During this time the egg begins to develop as a mass of cells, going from a single large cell, to 2, 4, 8 and 16 before becoming more complex, all the while remaining basically the same size. When the embryo reaches the uterus, it is implanted and the placenta, the link between mother and baby- starts to grow. So preimplantation refers to this time that the embryo is traveling towards the uterus.

A very exciting discovery was that at the 4-cell stage (pictured above), a single cell could be lost, and the other three would be sufficient to grow into a healthy adult. When people choose to have in vitro fertilization, the 4-cell stage embryos can survive outside the body. One cell is removed and the DNA from this single cell is sequenced for specific genetic diseases or traits.

Here is a story of one such use. In this instance a genetic disease with a clear monogenetic origin was analyzed and only negative embryos were given to the mother. Of course, this kind of analysis can only be done when the egg is fertilized outside the body (i.e. in vitro fertilization). It is not possible to recover a fertilized egg from a woman, analyze it and then reinsert it.

There are many traits for which we know a single gene will change a persons appearance. However, in discussing this controversial technique, it is worth to keep in mind the complex origins of many diseases, let alone our appearance and intellect.

Image: Lorena on Flickr