New research now shows that sperm cells carrying the X chromosome and Y chromosome travel at different speeds. The X chromosome (determines the sex of the fetus as female) is slower than the Y chromosome (determines the sex of the fetus as male). This new information can help people in choosing the sex of their baby. However, it creates concerns as it may cause demographic instability as more people will opt to have sons.
What is the distinction between sperm cells?
Masayuki Shimada of Hiroshima University in Japan and his team found that within the X chromosome, 500 genes are active which are inactive in the Y chromosome.
Within these, there are proteins which are prominent on the outer layer of the sperm cell. Chemicals within the makeup of two of these proteins are what may cause the sperm cell to move slower. The Y chromosome moves at average speeds.
Scientists tested this theory on mice and found that offspring conceived with the fast sperm were 90% male. The slower sperm cells lead to the conception of pups that were 81% female. These results were seconded when this research was conducted on livestock (cows and pigs). Testing on humans has not happened yet but Shimada is convinced it will work.
However, it could take up to a decade to turn this theory into a commercial method for people to use.
Another method of distinguishing between the X and Y chromosome carrying cells also exists. George Seidel of Colorado State University added dye to the sperm cells that affect DNA. Y chromosome cells have less DNA; hence, they are duller and can be distinguished. This method, called “flow cytometry,” leads to a 93% possibility of having a girl, and an 82% possibility of having a boy.
Choosing the sex of your baby may cause a skewed sex ratio.
Such a method will have high demand in countries and regions where there is already a demographic imbalance in favor of males.
It will be highly successful as other methods of choosing the sex of a baby are expensive.
The chromosomes of IVF embryos can be studied before implantation to help determine the sex of the baby. This method called pre-implantation genetic diagnosis (PGD) has proven to be very reliable in choosing the sex of the baby as it is 100% effective.
PGD and flow cytometry are both expensive and require highly skilled professionals and specialized equipment, both of which are not available everywhere.
Sex selection by any method is prohibited in Australia, China, India, UK, and Canada to preserve a stable sex ratio. It is only allowed for medical purposes. However, it is permitted in most other countries (the USA included) for “family balancing.”
Shimada’s could make the process of sex selection easier and cheaper, hence more easily acquired. However, it may also be prone to misuse. If it is easily accessible, more individuals may use it to have boys rather than girls, creating a possibility for grave social consequences in the future.