Or perhaps a better question, who determines the gender of a baby? When using In-vitro Fertilization (IVF), or some other methods, parents can quickly determine and even select the baby’s gender. But how? What goes on in the gender determination process?
The gender development process is much longer than it is complex, and the following sections will delve into how male and female fetus development differ, occur, and end. Potential issues in development and ways to circumvent them will also be explained.
The General Idea
All live organisms have chromosomes in their bodies, and different species have different numbers. As for humans, we have 46 chromosomes: 22 pairs of non-sexual chromosomes, also known as ‘autosomes’, and one pair of sex chromosomes.
While the autosomes are identical for females and males, sexual chromosomes are not. In fact, females always have two X chromosomes, and males have an X and a Y.
When they mate, the mother passes on one of her sex chromosomes—along with half or 23 of her autosomes, as is the case with the father—and the father passes on his X or Y. This is why the father is always the one responsible for the sex of the child!
The Body Cycle
A sexually developed female will ovulate once a month halfway through her menstruation cycle—a cycle that lasts 28 days. Midway through, an egg is released from a female’s ovaries, containing the said autosomes and one sex chromosome.
After mating, the male’s sperms carrying the same number of autosomes and a sex chromosome try to reach the egg. The egg and sperm combine to create a new individual with, again, 44 autosomes and 2 sex chromosomes, and if the sperm carried an X, it is a boy.
A sex chromosome may be missing or damaged, resulting in a child with an abnormality; females with only on functional X have Turner’s Syndrome.
You can select the gender of the baby naturally and accurately.
Human Gender Differentiation
Even before the development of a fetus, gonadal steroid hormones initiate and control the sex differentiation process, wherein a fetus receives and develops characteristics that are male or female.
After the sixth week, differentiation starts, and becomes determinable by the ninth. Ultimately, all sexual traits and organs that pertain to the gender are formed.
When differentiation starts, an embryo has two ducts that are precursory embryonic structures: Wolffian and Mullerian. Wolffian ducts form the internal male reproductive system, and Mullerian ducts form that of female.
These precursors will develop into sex organs or disintegrate over the next weeks, depending on the pre-determined gender, as controlled by hormones.
Gender-specific Differentiation and Internal Development
Female sex organs are developed in the absence of the SRY-gene. This gene only acts on the Y chromosome, of which females have none.
The Wolffian ducts, defining male organs, will disintegrate, while the Mullerian ducts will develop. The latter will form female structures: uterus, cervix and fallopian tube. Gonads that remain undifferentiated form other structures: ovaries, vagina and labia, among others.
The opposite occurs for males. The SRY-gene, which is activated in the presence of a Y chromosome, initiates differentiation for male sex organs through chemical alterations in the fetus. Gonads then secrete an anti-Mullerian hormone, a protein that disintegrates the Mullerian ducts.
The Wolffian ducts, defining male organs, will develop male sex organs: seminal vesicles and vas deferens. Gonads that remain undifferentiated form other structures: testes, scrotum, and prostate gland, among others.
External genitals begin to differentiate during the ninth week, and end development by the 12th. The original tissue matter and structures differentiate and develop into male or female external organs.
During this process, the genital tubercle elongates to become a female’s clitoris or a male’s glans penis. The urethral fold becomes the female’s labia minora or the male’s ventral part of the penis and spongy urethra.
This development can be modified due to genotypic, environmental or hormone imbalance factors. As such, diagnoses and screening techniques were created to detect abnormal embryos.
One can diagnose the genetic condition, or present genetic errors, of the embryo before IVF implantation through Preimplantation Genetic Diagnosis (PGD). One can also look for potential risk factors based on chromosome conditions through Preimplantation Genetic Screening (PGS).