The genes that make up the blue print for an organism are carried on its DNA, which consists of a string with information coded much like letters and words. Genes or sets of genes determine many of the physical and biochemical characteristics of the organism – for example a gene for growth rate, or a set of genes that make a plant drought tolerant. Genetic sequencing is the determination of the precise DNA sequences that make up the genes of an organism (the Human Genome Project is the most famous example of this). Using this information, researchers can identify certain DNA elements that are associated with particular plant characteristics of interest (“molecular markers”). Breeders can then use these markers to quickly identify individual plants that have the desired characteristics without having to actually grow the plants in the field. Breeders choose individual plants for breeding that have the markers for the characteristics they need and quickly set aside the plants that do not. This is called “marker assisted selection” or “marker assisted breeding”. This technique allows breeders to cross-breed individual plants to efficiently and reliably add desired characteristics to particular crop varieties. By contrast, genetic engineering involves directly changing the DNA sequences to alter or add to the plants’ genes and create new characteristics.