Introduction

• Extranuclear inheritance or cytoplasmic inheritance is the transmission of genes that occur outside the nucleus.
• It is found in most eukaryotes and is commonly known to occur in cytoplasmic organelles such as mitochondria and chloroplasts or from cellular parasites like viruses or bacteria.
• Extracellular inheritance is a non-Mendelian inheritance wherein a trait was transmitted from the parent to the offspring not nuclear in nature but involving other organellar genetic material.
• There are traits manifested in certain eukaryotes that result from extranuclear inheritance.
• The mitochondria, for instance, contain genetic material independent of the chromosomes inside the nucleus.
• During the union of gametes, the mitochondrial DNA from the maternal parent is imparted to its offspring.
• Hence, when the mitochondrial DNA is expressed, the resulting traits would be extranuclear in nature, and determined largely as maternal effect. Inherited diseases relating to mitochondria is called mitochondrial disease.