X-linked recessive inheritance

Glucose-6-phosphate dehydrogenase (G6PD) deficiency in red blood cells X-linked recessive inheritance many specific mutations Common variants mild deficiency variant in African Americans, moderately severe deficiency variant in Caucasians of Mediterranean descent Frequency 1/10 males 1/100 males, African American and Mediterranean, respectively... 

As in X-linked recessive inheritance, male-male transmission of the disease-causing mutation is not seen Fig 11-1-8). 

The other modes of inheritance can influence the relative proportions of affected individuals who belong to one gender or the other (e.g., more affected males under X-linked recessive inheritance, more affected females under X-linked dominant inheritance), but they do not involve any differences in expression depending on the transmitting parent. 

This is an X-linked, recessive, inherited disorder associated with a virtually complete deficiency of hypoxanthine-guanine phosphoribosyltransferase and, therefore, the inability to salvage hypoxanthine or guanine. 

The answer is b. (Murray, pp 259-267. Scriver, pp 3827-3876. Sack, pp 97-158. Wilson, pp 287-320.) Metabolic diseases usually exhibit autosomal or X-linked recessive inheritance. Autosomal recessive inheritance is most likely because the affected patient is female. In this case, the parents are obligate carriers and there is a 1/4 chance (25% recurrence risk) that their next child will be affected. The symptoms suggest Tay-Sachs disease (272800), an autosomal recessive disorder involving severe neurodegeneration and early death. 

Copper deficiency is not a major public health concern in the United States. Copper deficiency is rarely observed in humans except in cases of severely malnourished children or those with Menkes disease - an X-linked recessively inherited disorder. This disease is a severe congenital copper deficiency marked by slow growth, progressive... 

X-linked recessive inheritance in females is impacted by a phenomenon known as X-inactivation or lyonization. A female s sex chromosomal constitntion is XX a male s sex chromosome constitntion is in XY. In females, a recessive disease mntation on one X chromosome should not resnlt in disease if the corresponding gene on the other X chromosome is normal. In actuality, the situation is more complicated. In females, one of the X chromosomes in each cell is randomly inactivated, a process known as X-inactivation. This is done to compensate for the donble state of X chromosomes in females relative to males. If the inactivation pattern is skewed so that the majority of X chromosomes with the normal gene are inactivated, the individual may be affected. The greater the skewed inactivation pattern, the more severe the disease. Becanse of this, the clinical phenotype of females with an X-linked recessive disorder, snch as ornithine transcarbamylase (OTC) deficiency, can range from nnaffected to severely affected. 

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