Complex sentence: Her work was groundbreaking: she developed the technique for visualizing maize chromosomes and used microscopic analysis to demonstrate many fundamental genetic ideas, including genetic recombination by crossing-over during meiosis--a mechanism by which chromosomes exchange information.
Split into simpler sentences: Her work was groundbreaking; she developed the technique for visualizing maize chromosomes and used microscopic analysis to demonstrate many fundamental genetic ideas. One of those ideas was the notion of genetic recombination by crossing-over during meiosis--a mechanism by which chromosomes exchange information.