Sex-linked traits are often expressed in different frequencies in males and females. This occurs because males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). Since many traits are carried on the X chromosome, any recessive trait present on an X chromosome will be expressed in males, who have only one copy of that chromosome. For females, having two X chromosomes means they would need to inherit the recessive trait on both X chromosomes to express it. This difference in chromosome composition leads to the varying expression of sex-linked traits between genders.
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