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During reproduction, two parents combine their genetic information via gametes to produce an offspring. Each diploid offspring inherits 22 autosomal chromosomes and one sex chromosome from each parent, creating a total of 44 autosomal chromosomes and a pair of sex chromosomes. Autosomal chromosomes are the same for males and females, but sex chromosomes are different and therefore determine the sex of the offspring.

In mammals, there are two types of sex chromosomes, X and Y. As we will discuss later in this section, an XY individual will be male, while an XX individual will be female. In other words, the presence of a Y chromosome determines 'maleness' in mammals. The central role of the Y chromosome in mammalian sex determination is supported by the presence of XXY males and XO females.





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