The discoveries of Sutton, Boveri, and others allowed a reexamination of Mendel's apparently forgotten publication. Mendel's laws are grounded in the chromosomal movements in meiosis, gametogenesis, and fertilization. Understanding the fundamental processes of cell division is the key to understanding Mendelian genetics. It is the process by which the somatic cells divide and maintain the same chromosomal complement. Mitosis is the process by which two identical daughter cells with identical DNA complements are formed from one progenitor cell.
Mutations can arise during DNA replication in mitosis, just as they do in meiosis.
These mutations, and their consequences in somatic cell diseases, such as cancer, are discussed in the molecular genetics lecture portion of this course. Most mitotic divisions, and consequently the fastest rate of growth, occurs before birth in the relatively protected environment of the uterus. Consequently, most genetic diseases are expressed at birth or during early development, although some late onset human diseases, and somatic cell diseases, do occur. Gelehrter, Collins, and Ginsburg, Chapter 2, should be read for a complete description of the events and importance of mitosis . Each somatic cell of a normal individual contains two copies of each of the 22 autosomal chromosomes, one of paternal origin and one of maternal origin, and either an X from the mother and an X from the father if the individual is female or an X from the mother and a Y from the father if the individual is male.