Handbook Of Neurodevelopmental and Genetic Disorders in Adults PDF
2.82 MB PDF
Matt Ridley (1999) beautifully described the genome when he referred to it as a book. Ridley wrote:
There are twenty-three chapters called chromosomes. Each chapter contains several thousand stories called genes. Each story is made up of paragraphs called exons which are interrupted by advertisements called introns. Each paragraph is made up of words called codons. Each word is written in letters called bases. There are one billion words in this book. This makes it longer than 800 Bibles. (p. 2)
The human genome contains 3,164.7 million chemical nucleotide bases consisting of four chemicals—adenine, thymine, guanine, and cytosine. The average gene consists of 3,000 bases, but sizes vary greatly, with the largest known human gene being dystrophin at 2.4 million bases. The total number of genes estimated in the human genome is 30,000– 5,000, much lower than previous estimates of 80,000–140,000. Of these nucleotide bases, 99.9% are exactly the same in all people. The functions of over 50% of discovered genes are still unknown. At least 50% of the human genome is made up of “junk DNA.” These are repetitive sequences that we believe have no direct function, but shed light on chromosome structure and operation. These repetitive sequences reshape the genome by rearranging it, creating entirely new genes, and modifying and reshuffling existing genes. It is believed that during the past 50 million years a dramatic decrease has occurred in the rate of accumulation and repeats in the human genome. Chromosome 1, which is likely the largest, contains nearly 3,000 genes; a Y chromosome contains the fewest (231). Fewer than 2% of the genome codes are for proteins. Humans share most of the same protein families with worms, flies, and plants, but the number of gene family members has expanded in humans, especially for proteins involved in development.
Since the publication of our volume Handbook of Neurodevelopmental and Genetic Disorders in Children (Goldstein & Reynolds, 1999), the tug of war in people’s acceptance of nurture and nature has continued. Despite increasing evidence of the power of human genes in shaping behavior, development, and life function, our society continues only reluctantly to acknowledge that there is a powerful biological basis for many behaviors. Yet our society is quick to embrace biological determinism for easily observed genetic conditions such as Down or Williams syndrome.
The present text grew out of our continued mutual interest in educating our students and fellow clinicians about the powerful role played by genetics in shaping all human behavior and achievement throughout the lifespan. We were also encouraged by the widespread adoption and acceptance of our child volume, the Handbook of Neurodevelopmental and Genetic Disorders in Children (Goldstein & Reynolds, 1999). Moreover, in our own search for information to assist our patients and their families as well as to educate our students, we have found a dearth of information on adult characteristics and outcomes, as well as on the changing interventions that may be required, for those with neurodevelopmental and genetic disorders first evident in childhood. It is our hope and intent that this text will at least help to remedy this problem and serve as a ready and comprehensive companion to our previous text on children, assisting clinicians to understand, evaluate, and ultimately assist people with genetic and neurodevelopmental disorders throughout their adult years.
In many ways, this work parallels the child volume: We provide a general introduction to the key issues involved in understanding etiology, evaluation, and treatment of the disorders covered, but we also provide a foundation for understanding related disorders that are not covered herein due to space limitations. The chapters that are disorder-specific follow an essentially common format for ease of reading, for reference use of the text, and for consistency in describing the various disorders reviewed. Although the focus of the volume is primarily on the adult presentation of the disorders covered in the child volume, we have also added some disorders that are often not prominent until at least early adulthood (e.g., the various progeroid syndromes), though they are preexisting in childhood.
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