What is meant by the ultimate fine structure mapping of a gene or a chromosome? What information does it provide & how it is likely to impact the study & application of Genetics?
-> The ultimate fine structure mapping of a gene or chromosome:
Recombination can serve as a useful tool for mapping genes. On the other hand, it is also possible to do genetic mapping without recombination. Though it requires more labors than the traditional recombination mapping, but it provides considerably more information. In fact, the ultimate in fine-structure genetic mapping is to obtain the nucleotide-pair sequence complete with the information of all nucleotide-pair changes that after the function of that genes or chromosome. Prior to 1975, the thought of trying to sequence entire genomes or chromosome was considered an uphill task, requiring years of work. By the end of 1976, Fredrick Sanger & his colleagues sequenced the entire 5,387 nucleotides long chromosome of a tiny phase Φ*174. Today, the entire chromosome of several viruses, including the complete 48,502 nucleotide-pair sequence of the phase λ chromosomes & segments of several eukaryotic chromosomes tens of thousands of nucleotide pairs in length have been sequenced. Within the next few years, the nucleotide sequences of hundreds of genes & the entire eukaryotic chromosomes would be determined & the information would be stored in computer data banks for future reference. The goal of the ‘Human Genome Project’ is to sequence the entire human genome in the coming decade or two.
First, it locates exactly the coding regions of all the genes. It provides the information that the spatial relationships among genes & the distance between them, to the exact nucleotide, without any guesswork about recombination frequency. It contains an open reading frame, i.e, a sequence of bases which if translated into one frame, contains no stop codons for a relatively long distance long enough to code for a polypeptide. In addition, an open reading frame must start with an ATG translation initiation codon.
Once the base sequence of DNA is known, from it one can also find out the amino acid sequence of a particular protein. Use the genetic code to translate the DNA base sequence of each open reading frame into the corresponding amino acid sequence.
Impact the study & application of genetics:
In human context, by knowing the chromosomal positions of genes for hundreds of genetic illness, the isolation of such defective DNA segments may be possible, the study of this aspect may help us know their corrective measures at the molecular level of the gene. It is hoped that the several persons suffering from diseases such as muscular dystrophy & cystic fibrosis may be cured.