Sense and antisense

A DNA sequence is called "sense" if its sequence is the same as that of a messenger RNA copy that is translated into protein.[19] The sequence on the opposite strand is called the "antisense" sequence. Both sense and antisense sequences can exist on different parts of the same strand of DNA (i.e. both strands contain both sense and antisense sequences). In both prokaryotes and eukaryotes, antisense RNA sequences are produced, but the functions of these RNAs are not entirely clear.[20] One proposal is that antisense RNAs are involved in regulating gene expression through RNA-RNA base pairing.[21]

A few DNA sequences in prokaryotes and eukaryotes, and more in plasmids and viruses, blur the distinction between sense and antisense strands by having overlapping genes.[22] In these cases, some DNA sequences do double duty, encoding one protein when read along one strand, and a second protein when read in the opposite direction along the other strand. In bacteria, this overlap may be involved in the regulation of gene transcription,[23] while in viruses, overlapping genes increase the amount of information that can be encoded within the small viral genome.

Chromosome diseases:

These diseases are caused by a major error in the DNA, with an entire chromosome having a problem. Chromosomes have hundreds and thousands of genes, so these diseases have major errors in the DNA code. The most common example is down syndrome.

About inheritance and genetics:

Inheritance of Nervous system disorders refers to whether the condition is inherited from your parents or "runs" in families. The level of inheritance of a condition depends on how important genetics are to the disease. Strongly genetic diseases are usually inherited, partially genetic diseases are sometimes inherited, and non-genetic diseases are not inherited. For general information,

Inheritance and Genetics of Nervous system disorders

Genetics of Nervous system disorders: Several diseases that directly affect the nervous system have a genetic component: some are due to a mutation in a single gene, others are proving to have a more complex mode of inheritance. As our understanding of the pathogenesis of neurodegenerative disorders deepens, common themes begin to emerge: Alzheimer brain plaques and the inclusion bodies found in Parkinson disease contain at least one common component, while Huntington disease, fragile X syndrome and spinocerebellar atrophy are all 'dynamic mutation' diseases in which there is an expansion of a DNA repeat sequence. Apoptosis is emerging as one of the molecular mechanisms invoked in several neurodegenerative diseases, as are other, specific, intracellular signaling events. The biosynthesis of myelin and the regulation of cholesterol traffic also figure in Charcot-Marie-Tooth and Neimann-Pick disease, respectively. (Source: Genes and Disease by the National Center for Biotechnology)