![]() ![]() Sperm cells do not have mitochondria therefore MtDNA is not present in these cells, meaning the father will only contribute nuclear DNA and will not contribute any mtDNA. The process of conception and the relative contribution of materials from the sperm and the egg can help explain the concept. It follows a pattern known as maternal inheritance. The inheritance of mtDNA is very different from the inheritance of nuclear DNA. Changes in mtDNA are another potential source of mitochondrial disease. Mitochondrial DNA (mtDNA) contains genes that code for a number of proteins that are used by mitochondria (i.e. Mitochondria have their own set of instructions, or blueprints-they have their own set of DNA. Mitochondria are of course the energy producing organelles in the body. The images below show possible scenarios:Īs seen above, it is only possible to inherit a recessive disease when a mutation exists on both sides of the family.Īs previously discussed, there are two sources of DNA in our body existing in two genomes-the nuclear DNA and mitochondrial DNA. This also means that at least one parent may also have the disease. Of the two alleles, one genetic change on one allele will result in the condition being expressed, even if the other allele does not have a genetic change. Like its namesake, autosomal dominant inheritance occurs because one allele “dominates” over the other. The chance of being affected with a disease depends on many factors which are outlined below. Genetic changes leading to disease are inherited in my different ways. However, some genetic changes (or mutations) can cause the gene to not function properly and thereby cause disease. Variation exists within everyone’s genes-that is how we are all different. These different gene versions are called alleles. ![]() An example is eye colour both parents have genes coding for eye colour yet the father may have the version for blue eyes and the mother may have the version coding for brown eyes. Both chromosomes contain the same genes and code for the same proteins, just slightly different versions of it. Recall that we have two copies of each chromosome-one from each parent. ![]() ![]() If there is a mutation in a nuclear gene in my parents, what are the chances of me inheriting the mutation or the disease? A small fraction of those nuclear genes code for mitochondrial proteins, therefore a mutation in one of these genes could lead to mitochondrial disease. An average human genome contains approximately 26 000 genes. It is organized into two sets of 23 chromosomes (one set from each parent). Our DNA inside the nucleus is our entire body’s blueprint which we inherit from both of our parents. The second is mitochondrial DNA (mtDNA) which is located in the organelle after which it is named. The first is the human genome located in the nucleus of the cell, where DNA is organized into structures called chromosomes. In a human cell there exist not one, but two full genomes. Wherever there is DNA, there is a potential source for a mutation. How a disease is inherited, depends upon where the mutation exists. An individual may inherit a mitochondrial disease in one of many ways. ![]()
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