With the development of physics, chemistry and biology, the application of new technology fully proves that chromosomes are composed of nucleic acids and protein, and the genetic material that constitutes genes is nucleic acids. Nucleic acids are divided into two categories: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is a carrier for storing genetic information (genetic code), which is relatively stable, can accurately replicate itself, maintain the genetic continuity of parents and offspring, guide protein synthesis, excavate metabolic process and character development, and produce genetic variation under certain conditions. However, the transmission of genetic information from chromosomes in the nucleus to cytoplasm outside the nucleus is also closely related to RNA. Genetic information is transcribed from DNA into RNA, and then RNA takes the genetic information outside the nucleus and sends it to protein.
The inheritance of human normal traits includes more than 20 kinds of pregnancy traits such as gender, body surface traits, physiological and biochemical characteristics and physical quality.