Question: Do you think mitrochondrial DNA is inherited separately? Is there anything other than the enzymes for respiration on it?

Caroline Dalton answered on 19 Jun 2012:

Mitochondrial genes are indeed inherited by a separate mechanism to the nuclear genes! Unlike nuclear DNA which is made up of genetic information from both the sperm and the egg (so the father and the mother), mitochondria and therefore mitochondria DNA is inherited only from the mother. The egg contributes all the mitochondria to the developing embryo and any mitochondria from the sperm which enter the egg are destroyed within the first couple of cell divisions after fertilisation. We therefore say that mitochondrial DNA is inherited maternally as it comes only from the egg cell from the mother.

The mitochondrial genome encodes 37 genes. Some of these are for proteins which form part of the respiratory chain but some others (tRNAs and rRNAs) are important for some steps in the process of making proteins from the genetic code. Interestingly the mitochondrial genome doesn’t actually encode all of the proteins needed for mitochondrial function. A lot of them are encoded by the nuclear genomes so you need both the nuclear and the mitochondria DNA to have functioning mitochondria!