What determines the sex of a newborn?

Baby girl? Or a baby boy? What do you think, if a couple is blessed with a baby girl, who is responsible for that? What determines the sex of a newborn?

Genetics has got the answer for this. Do you know, female alone is not responsible for the birth of a baby girl. Actually it’s the male who is responsible for it. Want to know how? Check this.

As we have already mentioned in our previous articles, human beings are diploid organisms (di-two, ploid-chromosome). Chromosomes are present in pairs. Each human cell consists of two sets of 23 chromosomes. Each set has similar homologs with an exception of sex chromosomes.

Read more on : How many chromosomes do Humans have?

In early 1891, it was observed that one of the chromosomes in males does not have a homolog. It was observed by considering some male insect species through microscopic analysis. This unpaired chromosome was called as X-chromosome. It was also observed that, it is present in all somatic cells of males but only in half of the sperm cells. So, their raised the question, which is the chromosome that is going to pair with this X-chromosome in sperm cells ??

As the analysis progressed, it was found that the case with the females is different. The females of the same species were found to have two X-chromosomes.

Later, the observations became clear that all the female species have two X-chromosomes (23rd pair) and the male species have one X-chromosome along with a morphologically different chromosome. It was later named as Y-chromosome.

This Y-chromosome pairs with the X-chromosome during meiosis in males because the X and Y chromosomes share a small region of homology. The constitution of these two X and Y chromosomes determine the sex at the time of fertilization.

The XX chromosomes represent the female and XY chromosomes represent the male.

So no matter what, if your daughter in law, or daughter or sister or any woman in your life is blessed with baby girl or baby boy, it’s not the woman who is responsible for this creation. It’s the man of her’s who is actually responsible for baby boy or baby girl. people are so obsessed with baby boy and its related beliefs that you often see lot of social evils happening because of the same. You might hear lot of cases about why my daughter in law is not able to give birth to baby boy ? probably this post will help you explain and may make you capable enough to explain others too.

In females only one type of gamete (X) is produced, hence it is known as Homogametic sex.  Whereas, males have two different type of gametes(X and Y) and is known as Heterogametic sex. Hence it is the male who is responsible for the determination of sex in the newborn. It is that sex chromosome which is passed from the male to the offspring that determines the sex of a child.

Let’s try to understand from figure above:

  1. Mother has XX chromosomes and Father has XY chromosomes.
  2. When Mother pass on X chromosome and Father also Pass on X chromosome then the child born will have chromosome XX and it will Baby Girl
  3. When Mother pass on X chromosome and Father also Pass on Y chromosome then the child born will have chromosome XY and it will Baby Boy

So the sex is determined by the type of chromosome is passed on by father as mother always passes X.