Preparation of genomic DNA from mammalian sperm.

Semen consists of spermatozoa and the seminal fluid, also called seminal plasma. This fluid is important for the survival of the spermatozoa, but may decrease the purity and thus quality of the DNA due to its fructose and protein content. In this protocol, spermatozoa are washed with ethanol to remove the fluid. The spermatozoa themselves are protected by a membrane rich in disulfide bonds, which impede cell lysis and thus hamper DNA isolation. To break disulfide bonds a strong antioxidant, such as dithiothreitol (DDT), is necessary. Similar to other protocols for DNA isolation from other mammalian tissues, proteinase K and SDS are included in the lysis reaction. After lysis of the sperm cells, the DNA is precipitated using ethanol and then redissolved in TE-buffer or ddH(2)O.