Knowra X-linked dominant inheritance X-linked dominant inheritance X-linked dominant inheritance is a pattern in which a disease-causing variant on the X chromosome can cause a trait or disorder when present in one copy. Its transmission and effects often differ between people with one X chromosome and those with two.
X chromosome : One of the human sex chromosomes, carrying genes involved in many traits beyond sex development. The variant’s location determines which relatives can inherit it and how it is transmitted.
Rett syndrome : A neurodevelopmental disorder usually caused by pathogenic variants in MECP2, with regression after early development. Most classic cases arise from X-linked dominant MECP2 variants and differ greatly by sex and mosaicism.
X-linked recessive inheritance : An inheritance pattern in which variants on the X chromosome usually cause disease when no functional copy compensates. Unlike dominant inheritance, heterozygous individuals often carry an X-linked recessive variant without typical disease.
Genetic counseling : A clinical process that helps people understand genetic conditions, testing, and reproductive or health choices. Counselors use family history and variant data to estimate relatives’ chances of inheriting a disorder.
X-inactivation : The process that largely silences one X chromosome in each cell of most individuals with two X chromosomes. Uneven silencing can shape symptom severity in heterozygous individuals.
Incontinentia pigmenti : A disorder affecting skin, teeth, hair, and sometimes eyes or the nervous system, usually caused by IKBKG variants. Its often severe effects in males illustrate how sex and variant context influence an X-linked dominant disorder.
Autosomal dominant inheritance : An inheritance pattern in which one disease-causing variant on an autosome can produce a phenotype. Autosomal variants can pass from father to son, unlike X-linked variants.
Cascade testing : Targeted genetic testing of relatives after a disease-causing variant is identified in a family. Testing can identify relatives who inherited the same X-linked variant.
Hemizygosity : The state of having only one copy of a particular chromosome region or gene. A single X-linked variant is not paired with a second X-linked allele in many males.
X-linked hypophosphatemia : An inherited phosphate-wasting disorder commonly caused by variants in PHEX, leading to rickets or osteomalacia. Affected fathers transmit the variant to all daughters and no sons, a clear family-pattern example.
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