Is it possible to freeze and successfully unfreeze a living person? Will you be able to choose the color of the eyes and hair of your future baby? How is the beauty of an embryo related to the beauty and intelligence of the child that will come out of it?
In the embryology laboratory we cryopreserve, that is, we freeze both germ cells and embryos at different stages of development. The essence of freezing is that we must pause all biological processes in cells. And we successfully achieve this by cooling to a liquid nitrogen temperature of minus 196 °C.
We can do this in two ways. Reduce the temperature quickly (this is vitrification, or ultra-fast freezing) or lower it slowly. Both techniques aim to avoid the formation of intracellular ice crystals, which can damage the cell.
This is possible when intracellular water leaves the cell and is partially replaced by special substances – cryoprotectors.
By using different concentrations of cryoprotectants and cooling rates, optimal conditions for this replacement are created.
In our body, cells vary greatly in their size, protein, fat and carbohydrate content. And all these factors will influence the rate of cell dehydration during cryopreservation and, accordingly, require different cryoprotectants, their concentrations and cooling rates.
In the laboratory, we freeze specific types of cells according to certain protocols, for which these protocols are developed. It is impossible to create one “universal” and effective for all types of cells in the human body. Therefore, at this stage of the development of science, we are not talking about freezing and safely thawing the whole organism.
2. Is it possible to choose the color of eyes or hair for an unborn child?
Today, genetic testing is used quite widely. It is performed after unsuccessful IVF attempts, in patients of the older age group, in order to avoid transfer of an embryo with chromosomal abnormalities into the uterine cavity. Such embryos are not able to implant, or can lead to miscarriage and early miscarriage, or to the birth of a child, for example, with Down syndrome.
Testing is also performed if there are cases of a genetic disease or its carriage in the family, for example, hemophilia, ichthyosis. Preimplantation genetic testing (PGT), like any medical procedure, has certain indications.
The testing itself consists of two stages – an embryo biopsy and subsequent genetic research. Fetal biopsy is an invasive procedure, meaning it involves entry into the body and associated risks. Obviously, it shouldn’t be done without good reasons. And the choice of eye and hair color is certainly not an important reason.
But there are other difficulties associated directly with genetic research: these traits are polygenic.
Firstly, several genes are responsible for this pigmentation. And secondly, their interaction is related to the environment.
That is, even if this analysis is carried out, it will still be extremely difficult to determine the real color of a person’s eyes and hair.
3. Boy sperm are said to be lighter than girl sperm. Therefore, they can be weighed or unscrewed in a centrifuge, and the gender of the baby will be immediately clear.
The father is entirely responsible for the sex of the unborn baby. Each person has 23 pairs of chromosomes, 46 in total. One of the pairs is sex chromosomes. A woman has two X chromosomes; therefore, all her eggs contain only X chromosomes. In men, a pair of sex chromosomes is represented by X and Y chromosomes, respectively, a sperm can carry either an X or a Y chromosome.
The X chromosome consists of approximately 150 million nucleotide pairs, and the Y chromosome consists of 60 million nucleotide pairs. However, the difference in the mass of chromosomes will have virtually no effect on the total mass of the sperm, since the latter contains organelles and parts that are much more significant in terms of their mass.
The shape of the sperm will largely determine its mass. The head is slightly larger or smaller, the tail is slightly longer or shorter, the presence of a cytoplasmic drop on the neck – all these parameters will give a more significant change in the mass of the sperm than the sex chromosomes. So you won’t be able to weigh or spin sperm in a centrifuge to select sperm of a certain sex.
To date, the only way to determine the sex of an embryo is preimplantation genetic testing (PGT). However, at the legislative level, the selection of embryos based on gender is prohibited. The exception is hereditary diseases linked to sex.
4. A “beautiful” embryo is always a beautiful and smart child. And an embryo of lower quality is automatically some kind of problem baby.
There is no direct correlation between the external parameters of the embryo and the health, much less the intellectual status of the baby.
As an example, consider blastocysts, which grow from abnormally fertilized eggs. For example, 3PN zygotes, which contain 69 chromosomes instead of 46, can turn into a very beautiful embryo on days 5-6 of development. But it is absolutely impossible to transfer such an embryo.
Also, when conducting preimplantation genetic testing, we can get results when the most beautiful embryo has genetic abnormalities, and the embryo is of lower quality, on the contrary, without chromosomal damage.
The baby’s health will depend on the health of the expectant mother and father, the course of pregnancy, childbirth and the postpartum period.
Regarding intellectual abilities, there are studies that show that children born after IVF are ahead in their development of children conceived naturally.
Scientists have come to the conclusion that this is due to the fact that the child after IVF is planned and long-awaited. Most often, his parents consciously approach pregnancy already in adulthood, so after his birth they invest in his development much more actively.
5. Is the sex of the child visible through a microscope?
Through the microscope located in the embryology laboratory, the sex of the unborn child is not visible. But if we need to understand whether we have a boy or a girl (for example, so that a child is not born with a genetic pathology linked to sex), then we must conduct a genetic study of the embryo.
To do this, the embryologist performs a biopsy of trophectoderm cells, that is, he plucks off a certain number of cells from the outer shell of the embryo, and sends this material to geneticists.
And this is where the magic happens: when using comparative genomic hybridization or next-generation sequencing, geneticists actually see the sex of the future person, although not in a microscope, but on a computer monitor.