Jumping Genes-“The Other Half of the Human Genome” and the Missing Heritability Conundrum of Human Genetic Disorders

Almost 45% of the human genome is composed of transposons with about 4 million copies. The retrotransposons constitute 42% of the human genome with active families (Long Interspersed Nuclear Element, SINE-R, VNTR, and Alu) allied with insertional mutagenesis and diseases. There are >500,000 L1 copies which represent ~17% with less than 100 active copies and are inserted in the human genome; >1 million Alu copies referred to as “a parasite’s parasite” and ~3,000 SVA (SINE-R, VNTR, and Alu) copies. Some Human Endogenous Retroviruses are still active in humans. Nonactive DNA transposons embody 3% of the human genome. TEs are known to engender genomic instability and reorganize gene expression system in germline as well as the somatic cells. The amended retrotransposon expression or function appears to be associated with stress, alcohol, neurodegeneration and aging. This review highlights recent findings on the role of jumping genes in human genetic disorders like cancer, autoimmune and neurological diseases.