“How a baby can have three biological parents”?-we often get curious when this sort of question arises in our mind. But it’s true indeed that it is possible. More or less we all are quite familiar with the word surrogacy, but what that surrogacy actually mean, does it only mean to carry a baby for an intended parents or does that carrying womb has an influence on that implanted embryo. It’s really crazy to find out the truth whether the baby will only bear the characters of its intended parents or both its parents and surrogate mother (gestational carrier).
Surrogacy is basically of two types. One of which is Traditional surrogacy and other is Gestational surrogacy. Traditional surrogacy is the one where sperms are collected from intended father, which is then artificially combined with the egg of surrogate mother. However, Gestational surrogacy is more like natural parenthood where the intended parents can be the biological father and mother despite begetting their child. This is where the sperm is collected from intended father and the egg is harvested from intended mother. In this process, in vitro fertilization (IVF) takes place followed by intra uterine implantation.
Now, is this implantation simply, for nurturing the embryo, the answer would say no. There is a term called ‘Epigenetics’ which refers to the potentially heritable changes in gene expression rather than alteration of genetic code itself, due to the influence of environment. It is a biological mechanism that switches gene on and off. We basically, inherit the genetic code so our genetics is solely determined by the DNA we inherit from our parents. But the expression of this genetic code, to some extent is dependent on its environment. It is more likely the change in a phenotype than the change in a genotype. In surrogacy epigenetic information (that is not encoded in the DNA sequence of the intended parents) is transmitted from womb to the fetus through cell division. Behaviour, emotions, function of the immune system, metabolism pattern, health pattern etc. are the epigenetic changes that can be inherited from surrogate mother to the fetus.
Let us now reveal the truth behind this third biological mother. It is quite absurd, a baby will stay in a womb, but it will not take anything from it. As we all know that there develops a placenta during pregnancy which control the passage of substances from mother to fetus and vice versa. Placenta never allows blood and cell to pass from mother to fetus or the waste from the fetus to mother. But a few DNA can pass through the placenta from mother to fetus. This has effect on the child’s future life. There is a process called DNA methylation which takes place after implantation of embryo. It is essential for the development of embryo. Number of methylation which will take place is controlled by the environment. This methylation is responsible for this epigenetic change which leads to the alteration of the physical structure of DNA without changing the DNA sequence. This only affects the process, how cells ‘read’ genes. This process ‘how cells read gene’ or gene expression of the fetus is affected by the womb where it grows up. So, here the fetus will bear the genes of its intended parents but the instructions on the expression of those genes are got from the mother who carries the baby to term. This epigenetic information is passed from cell to cell during cell division.
How this DNA methylation does this epigenetic change is very simple. Methyl group is highly specific to cytosine nucleotide of DNA where it gets bound with the help of methyl transferase. This leads to the change in structure of DNA and modify the gene’s interactions with other substances inside the nucleus needed for translation. This is the subtle way how DNA changes its behaviour according to its environment.
There are many ways to change the external structure of DNA, where DNA methylation is one of such. This process of turning the gene on and off is responsible for building phenotypic characters of the baby. To conclude, technology has lessened, up many barriers and made things possible out of impossibilities. Surrogacy is one such instance where Epigenetics has flared up to prove that genetics can also be shaped by environment. Now, it is not at all outlandish to say that babies born through gestational surrogacy have three biological parents instead of two. But there is nothing to worry about, because the change is so small that it can hardly affect the child.
Fariha Tasnim is a student at the department of pharmacy, East West University, Bangladesh. She can be reached at firstname.lastname@example.org
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