Quiz 3

Ref: Robbins 8th 171, Harrison 19th p 451, 85e
Nemaline myopathy is inherited as autosomal recessive disorder. It is a clinical heterogeneous condition and not a mitochondrial disease. Five genes have been associated with this myopathy. All code for thin filament-associated proteins, suggesting disturbed assembly or interplay of these structures as a pivotal mechanism, mutations of the nebulin (NEB) gene account for most cases, including both severe neonatal and early childhood forms.

Ref: Harrison 19th p 2350
 Approximately 1/500 newborn males has a 47, XXY chromosome complement, representing the most common sex chromosomal aneuploidy in males. The incidence approximates 1% among the mentally retarded, clustering among patients with IQs greater than 50 and in infertile males.
 The chromosomal aberration most often results from meiotic nondisjunction of an X chromosome during parental gametogenesis; the extra X chromosome is maternal in origin in 54% and paternal in origin in 46% of patients.
 XX male is thought to occur in 1 in 20, 000 newborn males. Affected individuals have a male phenotype, small testes, a small phallus, and no evidence of ovarian or miillerian duct tissue; they appear, therefore, to be distinct from the ovotesticular disorder of sexual development. This disorder resembles Klinefelter syndrome, but stature is greater in the latter. Undescended testes and hypospadias occur in a minority of patients. The histologic features of the testes are essentially the same as in Klinefelter syndrome. Patients with the condition usually come to medical attention in adult life because of hypogonadism, gynecomastia, or infertility. Hypergonadotropic hypogonadism occurs secondary testicular failure.

Ref: Nelson 19th edition
Folate cofactors are one-carbon donors essential for the biosynthesis of purines and thymidylate. Mammalian cells are devoid of folate biosynthesis and are therefore folate
auxotroph that takes up folate vitamins primarily via the reduced folate carrier (RFC). The gene for RFC is located on chromosome 21.

Ref: Nelson 18th edition ch., 79 and Robbins-9 edition p 1
The human genome has approximately 25, 000 genes, which are the individual units of heredity of all traits The human genome contains roughly 3.2 billion DNA base pairs. These proteins variously function as enzymes, structural components, and signalling molecules and are used to assemble and maintain all of the cells in the body