Gene mapping vs. physical mapping Gene mapping

1 gene mapping vs. physical mapping

1.1 gene mapping
1.2 physical mapping
1.3 genome sequencing

gene mapping vs. physical mapping

there 2 distinctive types of maps used in field of genome mapping: genetic maps , physical maps. while both maps collection of genetic markers , gene loci, genetic maps distances based on genetic linkage information, while physical maps use actual physical distances measured in number of base pairs. while physical map more accurate representation of genome, genetic maps offer insights nature of different regions of chromosome, e.g. genetic distance physical distance ratio varies @ different genomic regions reflects different recombination rates, , such rate indicative of euchromatic (usually gene-rich) vs heterochromatic (usually gene poor) regions of genome.

gene mapping

researchers begin genetic map collecting samples of blood or tissue family members carry prominent disease or trait , family members don t. scientists isolate dna samples , closely examine it, looking unique patterns in dna of family members carry disease dna of don t carry disease don t have. these unique molecular patterns in dna referred polymorphisms, or markers.

the first steps of building genetic map development of genetic markers , mapping population. closer 2 markers on chromosome, more passed on next generation together. therefore, co-segregation patterns of markers can used reconstruct order. in mind, genotypes of each genetic marker recorded both parents , each individual in following generations. quality of genetic maps largely dependent upon these factors: number of genetic markers on map , size of mapping population. 2 factors interlinked, larger mapping population increase resolution of map , prevent map being saturated .

in gene mapping, sequence feature can faithfully distinguished 2 parents can used genetic marker. genes, in regard, represented traits can faithfully distinguished between 2 parents. linkage other genetic markers calculated same way if common markers , actual gene loci bracketed in region between 2 nearest neighbouring markers. entire process repeated looking @ more markers target region map gene neighbourhood higher resolution until specific causative locus can identified. process referred positional cloning , , used extensively in study of plant species.

physical mapping

since actual base-pair distances hard or impossible directly measure, physical maps constructed first shattering genome hierarchically smaller pieces. characterizing each single piece , assembling together, overlapping path or tiling path of these small fragments allow researchers infer physical distances between genomic features. fragmentation of genome can achieved restriction enzyme cutting or physically shattering genome processes sonication. once cut, dna fragments separated electrophoresis. resulting pattern of dna migration (i.e. genetic fingerprint) used identify stretch of dna in clone. analyzing fingerprints, contigs assembled automated (fpc) or manual means (pathfinders) overlapping dna stretches. choice of clones can made efficiently sequence clones determine dna sequence of organism under study.

in physical mapping, there no direct ways of marking specific gene since mapping not include information concerns traits , functions. genetic markers can linked physical map processes in situ hybridization. approach, physical map contigs can anchored onto genetic map. clones used in physical map contigs can sequenced on local scale new genetic marker design , identification of causative loci.

macrorestriction type of physical mapping wherein high molecular weight dna digested restriction enzyme having low number of restriction sites.

there alternative ways determine how dna in group of clones overlaps without sequencing clones. once map determined, clones can used resource efficiently contain large stretches of genome. type of mapping more accurate genetic maps.

genome sequencing

genome sequencing mistakenly referred genome mapping non-biologists. process of shotgun sequencing resembles process of physical mapping: shatters genome small fragments, characterizes each fragment, puts them (more recent sequencing technologies drastically different). while scope, purpose , process totally different, genome assembly can viewed ultimate form of physical map, in provides in better way information traditional physical map can offer.