As we first saw in Chapter 2, meiotic recombination between X-linked loci only occurs between the two homologous X chromosomes and is, therefore, restricted to females. X-linked loci do not participate in meiotic recombination in males, who have a Y chromo some and only one X chromosome. There are, however, a small number of contiguous loci, located at the tips of the p and q arms of the sex chromosomes, that are homologous between X and Y and recombine in male meiosis. As a consequence, during spermatogenesis, a pathogenic allele at one of these loci on the X chromo some can be transferred onto the Y chromosome and passed on to male offspring, thereby demonstrating the male-to-male transmission characteristic of autosomal inheritance. Because these unusual loci on the X and Y mimic autosomal inheritance but are not located on an autosome, they are referred to as pseudoautosomal loci; the segments of the X and Y chromosomes where they are located are referred to as the pseudoautosomal regions.

One example of a disease caused by a pathogenic variant at a pseudoautosomal locus is dyschondrosteosis, a dominantly inherited skeletal dysplasia with disproportionate short stature and deformity of the fore arms. Although a greater prevalence in females than in males initially suggested an X-linked dominant disorder, the presence of male-to-male transmission clearly ruled out strict X-linked inheritance (Fig. 1). Variants in the SHOX or SHOXY gene, located in the pseudoautosomal region on Xp and Yp, respectively, are responsible for this condition.

Fig1. Pedigree showing inheritance of dyschondrosteosis due to variants in SHOX, a pseudoautosomal gene on the X and Y chromosomes. The arrow shows a male who inherited the trait on his Y chromosome from his father. His father, however, inherited the trait on his X chromosome from his mother. From Shears DJ, Vassal HJ, Goodman FR, et al: Mutation and deletion of the pseudoautosomal gene SHOX cause Leri-Weill dyschondrosteosis, Nat Genet 19:70–73, 1998.

اخر الاخبار

اخبار العتبة العباسية المقدسة

المجمع العلمي يواصل إقامة مسابقة الثقلين القرآنية لطلبة مدارس كربلاء

عضو مجلس إدارة العتبة العباسية المقدسة يطلع على آليات تطوير البرامج التعليمية في مجموعة العميد

مجموعة مناحل الكفيل تختتم مشاركتها في معرض السليمانية الدولي للزراعة والصناعات الغذائية

لتوثيق التراث العلمي.. وفد قسم شؤون المعارف يلتقي عددًا من أعلام مدينة النجف

المزيد

الآخبار الصحية

ثورة طبية.. الذكاء الاصطناعي يكشف سرطان الكلى في وقت قياسي

لتعزيز الطاقة والتغلب على التعب.. عليك بـ7 طرق بسيطة

لتحسين الهضم والتحكم في الشهية.. ما أفضل وقت لتناول التمر؟

خبراء يكشفون تأثير الاستحمام في الظلام على جودة النوم !

المزيد

الآخبار التكنلوجية

إزالة ثاني أكسيد الكربون من الغلاف الجوي.. ما دور المحيطات والبحار؟

نظائر الهيليوم مقياس لاكتشاف رواسب الذهب.. كيف ذلك؟

الصين تطلق أول ناقلة نفط خام ذكية في العالم تعمل بالميثانول

الزمن على المريخ أسرع من الأرض.. دراسة علمية تكشف الفوارق

المزيد

مواضيع ذات صلة

Human Hemoglobin and Associated Diseases

The Relationship Between Genotype and Phenotype in Genetic Disease

Effect of Pathogenic Variants on Protein Function

HNF1A and HNF4A (Transcription factor MODY)

Categories of Epigenetic disorders

Epigenetics in Development

Mosaicism

Characteristics of autosomal recessive inheritance

Patterns of Inheritance

Pedigrees

Genotype and Phenotype

Genetics in the Diagnosis of Celiac Disease: Role of HLA DQ2 and DQ8