129 4.3 Linkage maps sons for mapping are to understand gene function and gene evolution, and to facilitate strain building. 1. Gene function. How can knowing the map position of a gene contribute to understanding its function? Essentially map position provides a way of “zeroing in” on a piece of DNA. If the genome of an organism has not been sequenced, the map position can provide a way of physically isolating the gene (this is called positional cloning , described in Chapter 11). Even if the genome has been completely sequenced, the phenotypic impact of most of the genes in the sequence is not understood, and mapping provides a way of correlating the position of an allele of known phenotypic affect with a candidate gene in the genomic sequence. Map position can be important in another way. A gene’s location is sometimes important for gene function because the location can affect the gene’s expression, a phenomenon generally called a “neighborhood effect.” Genes of related function are often clustered next to one another in bacterial chromosomes, generally because they are transcribed as one unit. In eukaryotes, the position of a gene in or near heterochromatin can affect its expression. 2.
This is the end of the preview. Sign up
access the rest of the document.
This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.