Final answer:
The alleles for sex-linked traits are inherited in a different pattern for males and females. For males, a single copy of an allele on the X chromosome will be expressed, while for females, two copies of an allele are present and the dominant allele will be expressed unless it is not present.
Step-by-step explanation:
The alleles for sex-linked traits are inherited in a specific pattern. Sex-linked traits are determined by genes located on the sex chromosomes. In humans, these chromosomes are X and Y. The X chromosome is larger and carries more genes, including those for many traits. The Y chromosome is smaller and carries fewer genes.
The inheritance of sex-linked traits follows a specific pattern. If a trait is carried by a gene on the X chromosome, it is considered a sex-linked trait. Males have one X and one Y chromosome, while females have two X chromosomes. As a result, the inheritance of sex-linked traits is different for males and females.
In males, because they have only one X chromosome, a single copy of an allele on the X chromosome will be expressed, regardless of whether it is dominant or recessive. So, if a male inherits an allele for a sex-linked trait, it will be expressed because there is no second copy to override it. On the other hand, in females, both X chromosomes are active, so two copies of an allele are present. If one X carries a dominant allele and the other carries a recessive allele, the dominant allele will be expressed. However, if the dominant allele is not present, the recessive allele will be expressed.
Learn more about Inheritance of alleles for sex-linked traits