Adding deoxyribonucleic acid (DNA) to an organism by artificial means does not in itself pose an ecological risk. Most populations of organisms vary considerably among individuals in the complement of genes carried in the DNA. The difference between genetically engineered organisms and their nonengineered counterparts is usually only one gene or a handful of genes. Genetically engineered organisms have new genes, placed into their DNA using molecular technology, that they would not have by traditional breeding methods. Because such a small fraction of genes is typically altered by genetic engineering, the possible risks or ecological effects of this new technology lie with the particular effects these novel genes have on the physical and physiological characteristics (the phenotypes) of the newly transgenic carriers. Though only a small amount of DNA may be involved, small changes in DNA can have profound effects.