Human sexuality

Question

Why do you get a girl or boy? But couldn't you do something to make sure you had a girl or boy without taking some tests?

Answer

Casey, Sex is determined by two chromosomes of the 24 that are in the nuclei of the human cell. Girls have two X chromosomes and boys have one X chromosome and one Y chromosome. The presence or absence of the Y chromosome dictates whether or not a baby is a boy or girl. Because prior to fertilization, the male chromosomes split, one half has the X chromosome and the other half has the Y chromosome and both become sperm, capable of uniting with a female egg. The female chromosomes split prior to fertilization but both halves contain the X chromosome. One one of the female halves form into an egg and only one egg is produce for fertilization. Only one sperm can unite with the egg. It's pure chance which half of the male chromosomes unite with the egg. Because the re-combination occurs in a random manner depending on which sperm reaching the egg first, it is not possible to screen for a boy or a girl. Once the egg is fertilized, you can test for the sex of the child.