Sex-Limited, Linked, and Influenced Traits

Some traits are carried on the sex chromosomes, X and Y. Most traits carried are present on only the X-chromosome. The Y-chromosome is smaller, and so, very few genes are located on this chromosome.

Sex traits can be categorized into three types of inheritance: sex-limited, sex-linked, and sex-influenced. Sex-limited traits are traits that are visible only within one sex. For instance, barred coloring in chickens normally is visible only in the roosters.

Sex-linked traits would be considered traits like sickle cell anemia and color blindness. They are said to be linked because more males (XY) develop these triats than females (XX). This is because the females have a second X gene to counteract the recessive trait. Thus, the trait is more likely to be visible in the male.

Sex-influenced traits are autosomal traits that are influenced by sex. If a male has one recessive allele, he will show that trait, but it will take two recessive for the female to show that same trait. One such gene is baldness.

A lot of sex-limtied traits can determine parental carriers by using a pedigree. The colored blocks indicate a recessive trait phenotype, and from there, carriers can be traced back. This is an effective method when determining the probability of an offspring receiving that trait.


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