Name: x- and y-linked disorder patterns
Uploaded: 2025-10-23T11:47:17.000Z
Duration: 1 min 43 s
Channel: JoVE

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Sex-linked Disorders

Some inherited disorders are caused by mutations to a single gene. And when located on a sex chromosome, the disorder is said to be sex-linked. Depending on which sex chromosome the gene is located on and whether one or both copies are required for proper function, these disorders are considered either Y-linked, X-linked dominant or X-linked recessive.

First, Y-linked disorders such as Y chromosome infertility are caused by mutations on genes located on the Y chromosome and can only be passed down from father to son. Second, X-linked dominant disorders including Fragile X syndrome require only one copy of the mutated gene, affect both females and males and cannot be passed from fathers to sons. Lastly, X-linked recessive disorders affect males much more often because females need two copies of the mutated gene.

Yet, unaffected heterozygous women can be carriers and have a 50% chance to pass it on to their sons. For example, an X-linked recessive disorder called Duchenne Muscular Dystrophy or DMD almost exclusively affect boys. DMD is caused by mutations in the gene encoding dystrophin, a protein involved in the proper contraction and repair of skeletal and cardiac muscle cells. These mutations can lead to structural or functional changes to the dystrophin protein without which muscle cells weaken and eventually atrophy.

sex-linked disorders

Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in biological deficits, the disorder is considered sex-linked.

Y chromosome mutations are called &#8220;Y-linked&#8221; and only affect males since they alone carry a copy of that chromosome. Mutations to the relatively small Y chromosome can impact male sexual function and secondary sex characteristics. Y-chromosome infertility is a disorder that affects sperm production, caused by deletions to the azoospermia factor (AZF) regions of the Y chromosome. In general, Y-linked disorders are only passed from father to son; however, because affected males typically do not father children without assisted reproductive technologies, Y-chromosome infertility is not typically passed on to offspring.

X-linked disorders can be either dominant or recessive. X-linked dominant disorders are the result of a mutation to the X chromosome that can affect either males or females. However, some disorders, including Fragile X syndrome, affect males more severely than females, likely because males do not have a second, normal copy of the X chromosome. Fragile X syndrome is characterized by a wide range of developmental problems, including learning disabilities. X-linked hypophosphatemia is another X-linked dominant condition that manifests in a vitamin-D-resistant form of Rickets.

For a recessive mutation to cause biological deficits, both copies of a chromosome must be mutated. As a result, females must receive two mutated X chromosomes to display an X-linked disorder. In contrast, males are affected if their single X chromosome carries the mutation. As a result, males are affected more often by X-linked recessive conditions, including color blindness, Duchenne muscular dystrophy, and hemophilia.

Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in biological ...

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KEY TERMS AND CONCEPTS

x- and y-linked disorder patterns

X- and Y-linked disorders come from mutations in genes on the sex chromosomes. These genes, like those on autosomes, are needed for normal body function. When a mutation causes a biological problem, the condition is called sex-linked.

Y-linked disorders come from changes in the Y chromosome. They affect only males, because only males carry a Y chromosome. Mutations in this small chromosome can affect male sexual function and secondary sex characteristics. One example is Y-chromosome infertility, which lowers sperm production because of deletions in the azoospermia factor, or AZF, regions of the Y chromosome.

Y-linked disorders are usually passed from father to son. In many cases, affected males do not father children without assisted reproductive technologies. Because of that, Y-chromosome infertility is not typically passed on to offspring.

X-linked disorders can be dominant or recessive. X-linked dominant disorders come from a mutation on the X chromosome and can affect males or females. Fragile X syndrome is one example. It can cause a wide range of developmental problems, including learning disabilities, and it often affects males more severely because they do not have a second normal X chromosome. X-linked hypophosphatemia is another dominant condition, and it causes a vitamin-D-resistant form of rickets.

X-linked recessive disorders require both copies of a chromosome to carry the mutation for females to show the condition. Males are affected if their single X chromosome has the mutation. That is why males are affected more often by X-linked recessive conditions such as color blindness, Duchenne muscular dystrophy, and hemophilia.

X- and Y-Linked Disorder Patterns

genetic lingo

Genotype, Phenotype, and Inheritance

Genotype, phenotype, and inheritance help explain how traits and disease risk are passed from parents to offspring. In diploid organisms, including humans, most other animals, and many plants, somatic cells carry a duplicate set of chromosomes. These chromosome pairs are homologous, with similar length, centromere position, and gene locations. Diploid organisms inherit two versions of each gene, one from each parent. These versions are called alleles, and they sit at the same relative locus,...

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Pleiotropy is when one gene affects more than one trait. The SOX10 gene is a clear example because it can influence pigmentation, hearing, and intestinal movement. These traits may seem unrelated, but they can all be linked to the same gene change. In humans, a deleted region in SOX10 can cause Waardenburg Syndrome Type 4, or WS4. WS4 is an autosomal recessive disorder, which means a person usually inherits two altered copies of the gene. Common signs include a white forelock,...

X- and Y-linked disorders come from mutations in genes on the sex chromosomes. These genes, like those on autosomes, are needed for normal body function. When a mutation causes a biological problem, the condition is called sex-linked. Y-linked disorders come from changes in the Y chromosome. They affect only males, because only males carry a Y chromosome. Mutations in this small chromosome can affect male sexual function and secondary sex characteristics. One example is Y-chromosome...

x-linked traits

X-Linked Inheritance in Families

X-linked inheritance explains how traits on the X chromosome are passed through families. In most mammalian species, females have two X sex chromosomes, while males have one X and one Y. A mutation on one X chromosome may be masked in females by a normal allele on the other X. In males, that same mutation is more likely to show because there is no second normal X to balance it. Traits caused by changes on the X chromosome are called X-linked traits. Color blindness is a well-studied example.

x-inactivation

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chromosomal theory of inheritance

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Genes map to chromosomes, and this idea explains how Mendel’s inheritance patterns work. Gregor Mendel published his pea plant breeding results in 1866. He showed that physical traits follow predictable patterns. At the time, scientists did not yet know that genes existed. Mendel used the word "factors" for the hereditary units he studied. The details behind Mendel’s laws of segregation and independent assortment were still unknown for many years. In the late 1800s, better microscopes and...

key terms and concepts

Learn how X-linked and Y-linked mutations affect inheritance, with examples including Fragile X syndrome, Y-chromosome infertility, color blindness, and hemophilia.

X- and Y-Linked Disorder Patterns | JoVE K12

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X- and Y-Linked Disorder Patterns

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