Mendelian and Atypical Patterns of Inheritance

INTRODUCTION Mendelian inheritance is based on the transmission of a single gene on a dominant, recessive or X-linked pattern. Discoveries on DNA structure, the genetic code, the genome and the observation that some characters and hereditary diseases do not follow classical mendelian inheritance have led researchers to define other patterns of transmission, referring particularly to multifactorial and mitochondrial inheritance. Multifactorial inheritance is based on the synergy of genes and environmental factors. Extra nuclear mitochondrial heredity can only be transmitted by the mother whose cells contain a number of mitochondria. Several factors can modify the expected individual phenotypes.There will undoubtedly be important advances in our knowledge of the pattern of inheritance of characters and diseases given a better understanding of gene structure and role, interaction of genes between them and with the environment.