Non-Mendelian Genetics: Finding of Transposable Elements in Corns and Flies

The essence of Mendelian genetics is the rule of chromosome segregation and the independent assortment of different chromosomes. However, genes on the same chromosome do not obey these rules as they are linked. Chromosomal recombination and translocation can also result in deviations from Mendelian laws. One of the most aberrant genetic segregations can be seen in selfish DNA elements like transposonstransposon. The transmission of transposons is unpredictable since these transposons can move from one chromosomal position to another. This chapter will discuss the initial studies on genetic instability that led to the identification of mobile factors in Zea mays (corn, maizemaize) and Drosophila. The first part introduces Barbara McClintockMcClintock’s genetic experiments that led to the first proposal for the existence of mobile elements in corn. We will also discuss the molecular identification of the proposed mobile elements. Genetic instabilityGenetic instability caused by mobile factors was also found in Drosophila. The second part discusses the PM hybrid dysgenesisPM hybrid dysgenesis phenomenon that causes high mutation incidence from crosses between specific P and M strains. Next, we will discuss the molecular basis for hybrid dysgenesishybrid dysgenesis and the transpositiontransposition of the P elementP elementtransposition. The use of transposons as vehicles for gene cloning, transgenesis, and mutagenesis facilitated the opening of a new era of molecular genetics in Drosophila and other organisms.