Genetic Perspectives on Brain Development and Complexity
The detection and identification of macromolecular species amidst a vastly complex background is a major problem in neurobiology. Therefore, we wish to begin by making a few introductory remarks pertaining to present estimates of macromolecular complexity of the brain. Genes and their transcripts are the first and second orders respectively of the vast molecular complexity of the brain. The first measurements relevant to estimating the extent to which “single” copy DNA (scDNA or DNA which encodes most of the different proteins) is transcribed in mammalian organs were made about 14 years ago (Hahn, 1970; Hahn & Laird, 1971). These initial measurements, although confirmed by others (Brown & Church, 1971; Grouse, Chilton, & McCarthy, 1972; reviewed by Kaplan & Finch, 1982), were underestimates. But they nonetheless showed that very complex arrays of RNA species are present in eukaryotic cells and organs. We now know that in the mammalian brain (mouse and rat) at least 18–20% of the scDNA is transcribed as nuclear RNA (=~40% of the haploid coding capacity) (Bantle & Hahn, 1976; Chikaraishi, Deeb & Sueoka, 1978). Most of these different transcripts apparently reside in the nuclear RNA of neurons (Ozawa, Kushiya & Takahashi, 1980).
KeywordsSequence Complexity mRNA Species Postnatal Development Rare Class Class Poly
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