Determine offspring sex based on genes XX and XY chromosomes

/*
The male gametes or sperm cells in humans and other mammals are heterogametic and contain one of two types of sex chromosomes. They are either X or Y. The female gametes or eggs however, contain only the X sex chromosome and are homogametic.

The sperm cell determines the sex of an individual in this case. If a sperm cell containing an X chromosome fertilizes an egg, the resulting zygote will be XX or female. If the sperm cell contains a Y chromosome, then the resulting zygote will be XY or male.

Determine if the sex of the offspring will be male or female based on the X or Y chromosome present in the male's sperm.

If the sperm contains the X chromosome, return "Congratulations! You're going to have a daughter."; If the sperm contains the Y chromosome, return "Congratulations! You're going to have a son.";
*/

function chromosomeCheck(sperm) {
  //check to see if x or y is in sperm
  //if it includes y it is a male
  //if it includes x it is female
  
  if (sperm.includes('Y')){
    return "Congratulations! You're going to have a son."
  } else {
    return "Congratulations! You're going to have a daughter."
  }
}