(d) : Satellite $DNA$ is that part of repetitive $DNA$ which has long repetitive nucleotide sequences in tandem that forms a separate fraction on density ultracentrifugation. $DNA$ fingerprinting involves identifying differences in some specific regions in $DNA$ sequence called as repetitive $DNA$, because in these sequences, a small stretch of $DNA$ is repeated many times. These repetitive $DNA$ sequences are separated from bulk genomic $DNA$ as different peaks during density gradient centrifugation. The bulk $DNA$ forms a major peak and the other small peaks are referred to as satellite $DNA$. Depending on base composition $(A:T$ rich or $G:C$ rich), length of segment, and number of repetitive units, the satellite $DNA$ is classified into many categories, such as micro­ satellites, mini­satellites etc. These sequences normally do not code for any proteins, but they form a large portion of human genome. These sequences show high degree of polymorphism and form the basis of $ DNA$ fingerprinting. Since $DNA$ from every tissue (such as blood, hair­follicle, skin, bone, saliva, sperm etc.) from an individual show the same degree of polymorphism, they become very useful identification tool in forensic applications.