How is gender determined? Chapter 3.8 How is gender determined?

X and Y chromosome X and Y chromosome: all human traits are determined by 23 pairs of chromosomes. In female, the 23rd chromosome has 2 pair of chromosomes that look the same (X and X). In male, the 23rd chromosome has 2 pairs of chromosomes that look different (X and Y). Female = XX Male = XY

Female karyotype

Male karyotype

Gender The X and Y chromosome determine the gender of an organism. Gender is the sex of an organism.

Gametes Every sperm will have either X or Y chromosome (50% X and 50% of Y chromosome). Egg cell will have only X chromosome.

Results If a fertilized egg will have XX, then it’s a girl. If a fertilized egg has XY, then it’s a boy.

Why do egg cells contain only one X chromosome? As a result of meiosis, each egg cell receives only one X chromosome from the pair of X chromosomes in the female parent cell.

Checking concepts: Which chromosome determine gender?

Which parent is responsible for the gender of the offspring?

Fill in blanks: 1. The gender of offspring is controlled by chromosomes in the ___________________. 2. A female body cell contains two ___________________. 3. A __________________ cell can contain either an X or a Y chromosome. 4. A fertilized egg that has two X chromosomes will develop into a _______________.