GENE20001 Lecture Notes - Lecture 19: Microbiological Culture, Streptococcus, P1 Phage
Document Summary
* generalised transduction can be used for fine structure mapping (mutations can be mapped that may be in the same gene or adjacent genes) To do this a pair of (cid:862)reciprocal(cid:863) crosses is set up usi(cid:374)g two trp (cid:373)uta(cid:374)ts (trpa- and trpb-) cross. 1 & 2 are reciprocal with respect to trp loci. Then replicate onto minimal medium to determine the number which are also trp+ (screening for wiltype recipient). To obtain trp+ cotransductants, a recombination event must have occurred between trpa- and trpb- as both the donor and recipient were trp- * the frequency of wildtype recombinants in the two crosses determines both the order and map distance between the two trp mutations. * to map the distance we need to measure the amount of recombination between these two markers. * cross 1 provides the data to measure this distance (the data set with the minimal number of crossovers needs to be selected.
