《医学分子遗传学》课件_第八章 基因结构和表达变化与疾病的关系.pptVIP

基因结构和表达变化与疾病的关系 The four aspects of a disease process Etiology: two major classes of etiologic factors: intrinsic or genetic, and acquired (e.g., infectious, nutritional, chemical, physical). Pathogenesis: the mechanisms of its development morphologic changes: the structural alterations induced in the cells and organs of the body clinical significance: the functional consequences of the morphologic changes Genome survey The 46 human chromosomes (22 pairs of autosomal chromosomes and 2 sex chromosomes) between them house almost 3 billion base pairs of DNA that contains about 30,000 - 40,000 protein-coding genes. The coding regions make up less than 5% of the genome (the function of the remaining DNA is not clear) and some chromosomes have a higher density of genes than others Genes and diseases Researchers have identified more than 4,000 diseases that are caused by genetic variants. But having a genetic mutation that may cause disease doesnt always mean that a person will actually get that disease. Because you inherit a gene from each parent, having one disease gene usually does not cause any problems because the normal gene can allow your body to make the normal protein it needs. Relationship between the genes and diseases 一个基因的突变可以产生一个以上的表型：如DMD 和BMD。 一种表型可以是由于多个基因的突变引起的：如视网膜色素变性，LQT综合症等等。 并不是所有的基因突变都可以找到相应的表型。 Duchenne muscular dystrophy (DMD): Most frequent muscle disease in children: affects ~1 in 3,500 live born males Onset usually between 3-6 years of age. The boys have a progressive muscle weakness where they have an unsteady walk and most will never be able to run. They have a tendency to fall and difficulties in raising themselves from the floor; the Gower sign. DMD patients are wheelchair bound by the age of 13 years and suffer respiratory problems due to progressive weakening of the intercostal muscles. Life expectancy is around 20-25 years. Occasionally, manifesting carrier females are observed (?? inactivation of the normal X-chromoso