The other way of delivering genes is a microinjection method ICSI (intra-cytoplasmic sperm injection) used for an absorbent in the form of a very fine needle to act as electroportional manner, where they penetrate the genetic material into the cytoplasm or nucleus and the most ideal way is to use viruses as gene transfer vectors. There are two types of viruses, one DNA and the other RNA, and there are chemical variations between the two viruses, both being formed of nucleotide units, in addition to the precise sequence of rules of the virus. 'nitrogen. Most RNA viruses are not suitable for gene therapy because RNA cannot be combined with DNA in human cells, with the exception of retroviruses where viruses can convert RNA into DNA. This therefore proves that understanding the molecular biology of a cell and the functioning of genes could make an important difference in molecular medicine. Thus, genetics is more relevant to medicine than classical genetics, which relies solely on observable reproductive outcomes..