Gene deletion is a loss of genetic material that can lead to serious abnormalities in an organism. The absence of the gene can be caused by any number of features, including errors during meiosis, breaking, and translocation. Any animal can experience deletion of a gene, and it is sometimes associated with quite severe disorders and a shortened life span. The size of the material deleted, which can range from small to large, can have some effect on whether the disorder merely causes problems or results in fatalities. Many human genetic disorders are related to gene deletion, often of a specific gene.
Most people encounter the concept of gene deletion through its manifestation as a disorder. Absence of genetic material can create birth defects and may be related to some forms of cancer. Specific disorders, such as cri du chat, are relatively well known, while rarer deletions may cause a somewhat less well-defined array of symptoms. When deletion is as minor as the absence of a single base pair, it may not impair life heavily, but large sections of DNA that are missing can significantly reduce an organism's chances for survival. In some cases, gene deletion is also related to cancer.
Scientists often use gene deletion in animals to study a variety of disorders. By isolating a single factor, scientists can often determine the function of that section of genetic material. Genetically engineered mice that undergo planned mutations to turn off specific sections of genetic material are sometimes called knockout mice and can be used to further research on a number of human disorders. Frequently, this type of research animal is used to model specific disorders such as obesity or arthritis.
Loss of genetic material does not always have a negative effect on organisms. Sometimes, not having certain genes can make an animal smarter or less susceptible to a variety of disorders. In many cases, animals missing genetic material are not diseased but merely different. The survival of many knockout mice attests to the great variety of mutations possible.
Given that research on genes is relatively complex, it may be possible to discover what disorders are caused by this kind of genetic mutation by looking at people who have symptoms in common and figuring out what they share genetically. Juvenile Paget's disease, for instance, has been linked to gene deletion in this way. The precise function of every piece of genetic material is difficult to map out, so functional examples from organisms that actually lack a gene can give insight into what the genetic material does.