Final answer:
A sex-limited trait is a gene present in both sexes but only expressed in one sex due to hormonal differences, leading to sexual dimorphism. These traits can vary due to sex-linked genes, especially X-linked genes, which are found on the X chromosome.
Step-by-step explanation:
A trait that is found in both sexes, but exhibits different expression, perhaps due to hormonal differences, is a sex-limited trait. Sex-limited traits are genes which are present in both sexes but are expressed in only one sex, leading to differences in physical appearance or physiological functions that are not directly related to reproduction. For example, while both males and females have the potential capacity for facial hair growth, the expression of this trait is much more prominent in males due to the influence of sex hormones like testosterone. These traits contribute to sexual dimorphism, which is the presence of distinct physical characteristics between males and females of the same species other than their reproductive organs.
This difference in trait expression can vary across species and can be influenced by sex-linked genes, particularly those that are X-linked. X-linked genes are found on the X chromosome, which is one of the two sex chromosomes, with the other being the Y chromosome. In humans, females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). Thus, if a gene that affects a particular trait is located on the X chromosome, it could potentially show different patterns of inheritance and expression in males and females. Examples of sex-limited expression could be beard growth in males and breast development in females, whereas an example of a sex-linked trait could be red-green color blindness, which is more commonly found in males due to its X-linked inheritance pattern.