Haploid Mapping

Genetic analysis in fruit fly, Drosophila melanogaster and diploid eukaryotes is identified by analysis called Random Strand Analysis. Sperm cells are capable of carrying one chromatid of meiotic tetrad which can join with egg cells having one chromatid of meiotic tetrad. Four spores of species like yeast and chlamydomonas are referred as tetrad. The spores are separated during the time of mating. If a mutation occurs in entirely different genes, then tetrad gets separated and segregated as non parental ditype, parental ditype and tetra type.

Tetrad which has parents of entirely different genotype is referred as parental ditype. For instance, an Ascomycetes spore has ascospores of non recombinant type. Tetrad which has recombinants of entirely different genotype is referred as non parental ditype. like ascomycetes spore of recombinant type. Tetrad which has entirely four different genotypes viz. two parental and two recombinants are referred as tetra type. 

Tetrad analysis

Linkage between different types of genes is referred as tetrad analysis. This occurs as a result of sporulation. Tetrad analysis aids in confirmation of mutation caused by  phenotype. In addition, it also helps in interaction of gene prediction and strain construction.

Examples are model organism like Saccharomyces cerevisiae for genetics and cellular biology. Study of cellular processes like cell cycle, DNA duplication, recombination, cell division and cell metabolism is easy. This yeast is cultured in test tube and is analyzed by tetrad analysis. By this analysis. it is found that Saccharomyces cerevisiae has nearly 12 million base pairs. It is completely sequenced during human genome project.

Tetrad dissection

Tetrad dissection helps yeast geneticists. It serves as a vital tool as yeast can be used as model organisms. Colonies of spores are isolated after separation of yeast tetrad spores and its germination. Micromanipulation and modern microscopy permits to isolate separated single colonies. When haploid crosses over each other, then tetrad spores are formed by transferring diploids to sporulation media. Enzymes like zymolyase helps in ascus wall digestion. Micromanipulator needle helps in separation of tetrad spores which are then placed over the Petri plates. Micromanipulator needle is made of fiberglass and spores are attached to the needle by the formation of water meniscus amidst  needle and agar.