This Publication Is Searchable The Merck Manual of Diagnosis and Therapy Section 21. Special Subjects Chapter 286. Human development depends on genetic and environmental factors. The genetic information is carried in the DNA of the chromosomes and mitochondria.
Most diseases probably have some genetic component, the extent of which varies.
DNA's capacity to replicate constitutes the basis of hereditary transmission. DNA also provides the genetic code, which determines cell development and metabolism by controlling RNA synthesis. Each pair consists of one chromosome from the mother and one from the father. One pair, the sex chromosomes, determines a person's sex. The X chromosome carries genes responsible for many hereditary traits, whereas the small, differently shaped Y chromosome carries the genes that initiate male sex determination.