They knew the fundamentals of Genetics i.e. the factors determining the sex of a child, genetic defect in a childlike lameness. They said it was not due to any defect in the mother or, the father but in the ovum or sperm of the parents (an accepted fact today).
Ayurvedic acharya’s has great knowledge about genetics. Hereditary and congenital types of diseases are classified by Sushruta. Ayurveda mentioned different diseases like sthaulya (obesity), klaibya (impotence), prameha (diabetes) etc. which is due to defect in genetic component of a person. Prakriti (different types of personality) is also mentioned as concept of genetics.
Ayurveda described about genetic concept while classifying the diseases in various seven groups. It has been nomenclature as Adibala pravritta or Sahaja vyadhi. There are references available in respect to prameha as Kulaja vikara.
Acarya Charaka has described the whole genetics in three genetic units in the form of Beej (Germinal cell), Beejbhag (Chromosome) and Beejbhagavyava (Gene). He has explained that due to vikriti of bija, bijabhaga and bijabhagavayava of the couple, there will be vikriti or vyapada in the child depending on gender.
Hence Ayurveda advised Beej Sudhhi of the male and female body before planning to have a child and to take rejuvenation therapy to restore health which prevents the appearance of genetic disorder.