Di truyền học phân tử, DNA tái tổ hợp, và bộ gen CÔNG NGHỆ hoặc RFLP. RFLP mở rộng bản đồ hệ gen của con người đã được xây dựng. Điều này đang chứng minh rất hữu ích trong các dự án giải trình tự bộ gen của con người và là một thành phần quan trọng của các nỗ lực để hiểu được những bệnh khác nhau của một gen và multigenic. | MOLECULAR GENETICS RECOMBINANT DNA GENOMIC TECHNOLOGY 411 or RFLP. An extensive RFLP map of the human genome has been constructed. This is proving useful in the human genome sequencing project and is an important component of the effort to understand various single-gene and multigenic diseases. RFLPs result from single-base changes eg sickle cell disease or from deletions or insertions of DNA into a restriction fragment eg the thalassemias and have proved to be useful diagnostic tools. They have been found at known gene loci and in sequences that have no known function thus RFLPs may disrupt the function of the gene or may have no biologic consequences. RFLPs are inherited and they segregate in a mendelian fashion. A major use of RFLPs thousands are now known is in the definition of inherited diseases in which the functional deficit is unknown. RFLPs can be used to establish linkage groups which in turn by the process of chromosome walking will eventually define the disease locus. In chromosome walking Figure 40-11 a fragment representing one end of a long piece of DNA is used to isolate another that overlaps but extends the first. The direction of extension is determined by restriction mapping and the procedure is repeated sequentially until the desired sequence is obtained. The X chromosome-linked disorders are particularly amenable to this approach since only a single allele is expressed. Hence 20 of the defined RFLPs are on the X chromosome and a reasonably complete linkage map of this chromosome exists. The gene for the X-linked disorder Duchenne-type muscular dystrophy was found using RFLPs. Likewise the defect in Huntington s disease was localized to the terminal region of the short arm of chromosome 4 and the defect that causes polycystic kidney disease is linked to the a-globin locus on chromosome 16. H. Microsatellite DNA Polymorphisms Short 2-6 bp inherited tandem repeat units of DNA occur about 50 000-100 000 times in the human genome Chapter 36 . .
