TDF gene encodes a transcription factor that is a member of DNA-binding proteins. This protein is referred as Testis-determining Factor (TDF). It initiates male sex determination and known as sex-determining region Y protein (SRY). Cytogenetic location of TDF gene is Yp11.2, which is the short (p) arm of the Y chromosome at position 11.2. Molecular location of TDF gene is base pairs 2,786,855 to 2,787,682 on the Y chromosome. Thus, the approximate length of the TDF gene is 860 bp.
The longest gene of the human body is that of Duchenne Muscular Dystrophy on X chromosome. It is 24,000-kilo base pair long. It provides instructions for making a protein called 'dystrophin'. This protein is located primarily in skeletal muscles used for movement and in heart (cardiac) muscle. Small amounts of this protein are present in nerve cells in the brain.