Testis-determining factor

Okay, so you know how some people are boys and some people are girls, right? Well, the testis-determining factor is something in our bodies that decides whether we are going to be a boy or a girl before we are even born.

The testis-determining factor is a special gene that is found on the Y chromosome. You might remember learning about chromosomes in science class - they are like tiny little packages inside our bodies that hold all of our DNA, or genetic information.

When a baby is conceived, they get one set of chromosomes from their mom and one set from their dad. If they get a Y chromosome from their dad, along with an X chromosome from their mom, then they will develop into a boy!

The testis-determining factor is what makes this happen. Specifically, it helps the baby's body to develop testicles instead of ovaries. Testicles are the boy's reproductive organs, and they make special cells called sperm that can help make a baby later on.

So, long story short, the testis-determining factor is a special gene on the Y chromosome that helps determine whether a baby will be a boy or a girl. It's like a little instruction manual inside our bodies that helps make sure we develop the way we're supposed to.