CAJ #4: How does it all work?

Imagine being able to engineer your baby, to filter out all the possible medical problems, and perhaps enhance its intelligence, athleticism or looks. Genetic manipulation is indeed no longer just the stuff of science fiction. The rather colloquial term “Designer Baby”, which is mostly used by journalists and not by scientists, made its way from sci-fi movies and into the Oxford Dictionary, where it is defined as “a baby whose genetic makeup has been artificially selected by genetic engineering combined with in-vitro fertilization to ensure the presence or absence of particular genes or characteristics.” In other words, creating a healthy baby with optional preselected, nonmedical qualities by using embryo screening technologies. But how are Designer Babies made? To explain this as efficient as possible, I am going to first give you a step-by-step explanation before delving more deeply into the theory and exact techniques behind this concept.

Before doctors can even begin to verify the genetic makeup of embryos, a number of steps have to be successfully completed beforehand. 

1. An embryo has to be created in a laboratory using in-vitro fertilization (IVF). As most of you may know, IVF, which was first performed in 1978, is the term used to describe the process in which a baby is conceived outside the mother’s womb. This method has been giving otherwise infertile couples a chance to have a baby of their own. For this, a woman’s eggs and a man’s sperm are being put together in test tubes to ensure fertilization. Zygotes (=the earliest developmental stage of an embryo) are formed. 
2. Within the first five days of the embryo’s creation, the zygotes reach the eight-cell stage. A single cell, called blastomere, is then carefully extracted to perform a process known as embryo biopsy. 
3. The cell is genetically analyzed /screened for genetic defects and chromosomal problems. 
4. After approximately 48 hours, after the results are available, healthy embryos (usually one or two) are implanted back into the woman’s uterus to develop. 

Short video to introduce the technology: https://www.youtube.com/watch?v=LjL2XoNIO54 

This genetic screening of embryos that is done prior to implantation is performed through a procedure known as preimplantation genetic diagnosis (PGD or PIGD), also referred to as preimplantation genetic screening or embryo screening. The innovative diagnosis technology involves the use of several genetic screening mechanisms, depending on the nature of the condition, such as Fluorescent In Situ Hybridization (FISH), Comparative Genomic Hybridization (CGH) or polymerase chain reaction (PCR) to help identify genetic and chromosomal abnormalities in embryos and thereby virtually ensure healthy outcomes. So far, this procedure, in combination with IVF, has been used to:

• check for specific genetic disorders; mainly for monogenic disorders (=disorders caused by a single gene) such as sickle cell disease, spinal muscular atrophy and Huntington disease, and for chromosomal abnormalities such as a balanced translocation or Down Syndrome. There are also infertile couples who choose to conceive through IVF and PGD so as not to pass on their inherited condition.
• increase the chances of a successful pregnancy (mostly for women aged above 35) and reduce spontaneous miscarriages by selecting an embryo that seems to have the greatest potential. Technical drawbacks such as the invasiveness of this procedure as well as the maternal age factor can sometimes work against the desired effect of PGD. 
• to preselect the sex of the baby for medical (when there is a higher risk for either to inherit a specific disease, such as X-linked diseases) and non-medical reasons such as for “family balancing”. Some genetic diseases are indeed specific to one of the genders, such as the disorder hemophilia which usually affects boys. In case there is a history of hemophilia in the family, only female embryos are chosen. 
• specifically select an embryo for the presence of a particular disability, such as deafness, so that the child would share the same characteristics with its parents. 
• to treat a sick sibling by selecting embryos that have the same tissue types as the sibling to become a suitable donor. These children are called “savior siblings” as their foremost purpose is to provide an organ or cell transplant to their siblings who suffer from diseases, such as leukemia or Fanconi anemia, that are only treatable with hematopoietic stem cell transplantation. For this, fertilized zygotes are tested for genetic compatibility and exclusion of genetic disorders. (See also the novel My Sister’s Keeper and its film adaptation)

PGD has first been successfully performed in 1989 and even though it is considered a highly controversial procedure, it became increasingly used during the 1990s to detect severe genetic diseases, such as Tay Sachs disease and Duchenne’s muscular dystrophy, and prevent them from being transferred to future generations. As it is only a recent development, this procedure does involve risks, such as premature birth, birth defects and developmental delays, but they have been rare so far. It is, however, a very invasive procedure that is prohibited in numerous countries, and one that is highly expensive. PGD could also be easily used to select traits like intelligence, height, looks and considerably more. The debate is over the ethical aspect and whether it should be legal to interfere with such characteristics when there is no medical reason to do so.

More on the technologies and the ethical side can be found in my next posts. Bye for now! ;-)