Describe the chromosomal mechanism of sex determination in humans. What are the possible combinations of chromosomes in the gametes produced by males and females, and how do these combinations lead to male or female offspring?

In humans, sex determination is primarily chromosomal, involving two sex chromosomes: X and Y. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). 

Gamete Production: 

Females (XX): During meiosis, females produce only one type of gamete (egg) with respect to sex chromosomes, which always carries an X chromosome. 

Males (XY): During meiosis, males produce two types of gametes (sperm) in approximately equal proportions: half carry an X chromosome and half carry a Y chromosome. Offspring Determination: When fertilization occurs, the sex of the offspring is determined by the sperm that fertilizes the egg: 

If an egg (X) is fertilized by a sperm carrying an X chromosome, the resulting zygote will be XX, developing into a female. 

If an egg (X) is fertilized by a sperm carrying a Y chromosome, the resulting zygote will be XY, developing into a male. Therefore, it is the male parent who determines the sex of the offspring in humans.