I am doing a project on the disorder MERRF in Mitochondrial DNA. I have to make a pedigree and explain how it is transferred on from generation to generation. I know that it is inherited maternally, but I am confused about how it is inherited. Would it be inherited inherited like autosomal DNA in a Mendelian fashion? If so, would this gene be dominant or recessive? Or would the children just automatically inherit whatever gene their mothers have? Also, how would the genotypes for Mitochondrial DNA be displayed? Any other useful information on Mitochondrial DNA or MERRF would also greatly appreciated. Thanks.
Even if the mitochondria were purely maternally inherited, a cell (including oocyte) typically contains many mitochondria and not all of the mitochondria may have the (deleterious) mutation. This phenomenon is called heteroplasmy.
MERRF is associated with a loss of function mutation in mitochondrial tRNAs (See NIH, Genetics Home Reference). The extent to which a cell will be affected would depend on number of mutated mitochondria it contains. Therefore different cells would be affected differently.
The trait inheritance would therefore not be in the typical Mendelian fashion.