Tetrad Analysis, Mitotic Recombination and Gene Conversion in Haploid Organisms (Fungi and Single Celled Algae)

In the previous section, we discussed the phenomenon of linkage and crossing over in diploid organisms. It may be recalled that chromosome mapping in diploids is mainly done with the help of three point test crosses. In haploids, detection of linkage and chromosome mapping is facilitated due to several reasons. Firstly, since a single allele per locus is present in a haploid, products of recombination can be studied without any complication due to dominance. Secondly, the life cycle of certain fungi e.g. Neurospora enables us to analyse the products of a single meiosis. Thirdly, in fungi like Neurospora, meiotic products are linearly arranged in the form of ordered tetrads, so that a distinction can be made between 'first division segregation' and 'second division segregation' permitting detection of crossing over between centromere and a gene.