X-Linked Recessive Inheritance: Characteristics and Examples

 

X-Linked Recessive Inheritance: Characteristics and Examples
X-linked recessive inheritance is a mode of inheritance in which a genetic disorder is passed down through genes located on the X chromosome. This pattern of inheritance affects males more frequently than females due to their unique sex chromosome composition, where they have one X and one Y chromosome. Females, on the other hand, have two X chromosomes, providing them with a higher chance of being carriers rather than displaying the disorder.

Characteristics of X-linked recessive inheritance include:

Males affected more frequently: Since males have only one X chromosome, if they inherit a faulty gene on that chromosome, they are more likely to express the disorder. This is because they do not have another X chromosome to compensate for the faulty gene.

Females as carriers: Females with one normal X chromosome and one X chromosome carrying the faulty gene are considered carriers. They usually do not display symptoms of the disorder themselves but can pass it on to their children.

Absence of father-to-son transmission: Affected fathers cannot pass the disorder directly to their sons since they pass their Y chromosome instead. However, affected fathers can pass the faulty gene to their daughters, who can become carriers.

Variable expression in carrier females: While carrier females typically do not show symptoms of the disorder, in some cases, they may exhibit milder forms of the disorder due to a phenomenon called skewed X-inactivation.

An example of a disorder in this category is Duchenne muscular dystrophy (DMD). DMD is characterized by progressive muscle weakness and is caused by a mutation in the dystrophin gene located on the X chromosome. Since males have only one X chromosome, if they inherit the faulty gene, they will develop DMD. Females who inherit the faulty gene become carriers and have a 50% chance of passing it on to their offspring.

In conclusion, X-linked recessive inheritance is a mode of inheritance where the genetic disorder is transmitted through genes located on the X chromosome. Males are more frequently affected, while females are typically carriers. Disorders such as Duchenne muscular dystrophy exemplify this inheritance pattern.

References:

National Human Genome Research Institute. (2021). Learning about X-Linked Recessive Inheritance. Retrieved from https://www.genome.gov/Genetic-Disorders/X-Linked-Recessive-Inheritance

Genetics Home Reference. (2021). X-linked recessive. Retrieved from https://ghr.nlm.nih.gov/primer/inheritance/xlinkedrecessive