Principles of Genetics and Breeding

1.2.3.8 Accurate transmission of genetic information

• A man is composed of an extremely large number of cells (60 trillion) that were produced by repeated mitosis of a single cell (a fertilized egg) and genetic information is precisely copied every time cell division is conducted. It is, therefore, possible theoretically to produce a man from a single cell. Individual genetic information was transmitted from our ancestors over hundreds of thousands of generations through reproductive cells. Hence, it is due to the accurate copy that a man’s offspring is a man.
• How is such an accurate copy possible? The key to the question lies on the structure of DNA. The replication of the DNA begins with the local separation of its complementary base pairs and each base on a single strand joins a complementary base (i.e. T-A, G-C) binding to the sugar phosphate on the outside. Each sugar binding to each new coming base combines with a neighboring phosphate, yielding a double-stranded DNA molecule. The other single-strand of DNA is also formed into a double-stranded DNA. The accurate replication is assured by the fact that only A-T and C-G base pairs are formed. These chemical combinations involve several different polymerizing enzymes called DNA polymerase. The resulting double-stranded DNA is exactly the same as the original DNA.