Final answer:
The X:A ratio, which is the ratio of the number of X chromosomes to the number of autosomes, is 1:1 in both females and males. This maintains equality in gene expression from the X chromosome as females inactivate one of their X chromosomes.
Step-by-step explanation:
In humans, the sex determination system is XY, with females having two X chromosomes (XX) and males having one X and one Y chromosome (XY). The X:A ratio, which is the ratio of the number of X chromosomes to the number of autosomes (non-sex chromosomes), is 1:1 in females since they have two X chromosomes and two sets of autosomes. In males, the ratio is 1:1 as well since they have one X chromosome and one set of autosomes.
The idea that one of the X chromosomes in females is inactivated and known as a Barr body, is crucial for understanding that both males and females effectively have one functional X chromosome in each cell. By understanding the chromosomal differences between males and females, we can determine the correct X:A ratio in each gender. In this case, the X:A ratio is 1:2 in females and 1:1 in males.