Outline the different patterns of inheritance associated with X linked genes. Where possible give a molecular explanation for the pattern. 6 th October 2008. X Linked Inheritance. Refers to the pattern of inheritance of a condition caused by a mutations in a gene located on the X chromosome.
6th October 2008
Allan-Herndon-Dudley Syndrome with X linked genes.
Androgen Insensitivity Syndrome
Colour Vision Deficiency
Congenital Hemidysplasia With Ichthyosiform Erythroderma And Limb Defects (CHILD)
Cornelia De Lange Syndrome
Duchenne And Becker Muscular Dystrophy
Emery-Dreifuss Muscular Dystrophy
Fragile X Syndrome
Glucose-6-Phosphate Dehydrogenase Deficiency
Paroxysmal Nocturnal Hemoglobinuria
Spastic Paraplegia Type 2
Spinal And Bulbar Muscular Atrophy
X-Linked Adrenal Hypoplasia Congenita
X-Linked Juvenile Retinoschisis
X-Linked Severe Combined Immunodeficiency
X-Linked Sideroblastic Anemia
X-Linked Spondyloepiphyseal Dysplasia TardaConditions Related To Genes On The X Chromosome
Hypohidrotic Ectodermal Dysplasia
Lenz Microphthalmia Syndrome
Mcleod Neuroacanthocytosis Syndrome
Opitz G/BBB Syndrome
Ornithine Transcarbamylase Deficiency
Otopalatodigital Syndrome Type 1
Otopalatodigital Syndrome Type 2
Reasons that a female may be affected with an X-linked recessive disorder
Affected males are rarely or never seen because of a lethal effect of the mutant allele in the hemizygous male.
Only females (and boys with Klinefelter Syndrome) are affected The pedigree may appear to have several spontaneous abortions in the offspring of affected females.
As a result the sex ratio of their live offspring is often skewed.
Examples include Incontinentia Pigmenti and Aicardi SyndromeX linked dominant inheritance with male lethality
In contrast to most other known X-linked recessive or dominant disorders, the milder phenotype of the males is unexplained. Possible explanations: