Autosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families.
An autosomal recessive disorder means two copies of an abnormal gene must be present in order for the disease or trait to develop.
Inheriting a specific disease, condition, or trait depends on the type of chromosome that is affected. The two types are autosomal chromosomes and sex chromosomes. It also depends on whether the trait is dominant or recessive.
A mutation in a gene on one of the first 22 nonsex chromosomes can lead to an autosomal disorder.
Genes come in pairs. One gene in each pair comes from the mother, and the other gene comes from the father.
Recessive inheritance means both genes in a pair must be abnormal to cause disease. People with only one defective gene in the pair are called carriers. These people are most often not affected by the condition. However, they can pass the abnormal gene to their children.
CHANCES OF INHERITING A TRAIT
If you are born to parents who both carry the same autosomal recessive gene, you have a 1 in 4 chance of inheriting the abnormal gene from both parents and developing the disease. You have a 50% (1 in 2) chance of inheriting one abnormal gene. This would make you a carrier.
In other words, for a child born to a couple who both carry the gene (but do not have signs of disease), the expected outcome for each pregnancy is:
A 25% chance that the child is born with two normal genes (normal)
A 50% chance that the child is born with one normal and one abnormal gene (carrier, without disease)
A 25% chance that the child is born with two abnormal genes (at risk for the disease)
Note: These outcomes do not mean that the children will definitely be carriers or be severely affected.
The inheritance of a trait encoded in the mitochondrial genome. Because of the oddities of mitochondria, mitochondrial inheritance does not obey the classic rules of genetics. Persons with a mitochondrial disease may be male or female but they are always related in the maternal line and no male with the disease can transmit it to his children.
Image source: zmescience.com
The mitochondria are normal structures or organelles in cells. They are located in the cell's cytoplasm outside the nucleus.
The mitochondria are responsible for energy production. They consist of two sets of membranes, a smooth continuous outer coat and an inner membrane arranged in tubules or in folds that form plate- like double membranes (cristae). The mitochondria are in fact the principal energy source of the cell (thanks to the cytochrome enzymes of terminal electron transport and the enzymes of the citric acid cycle, fatty acid oxidation, and oxidative phosphorylation). The mitochondria convert nutrients into energy as well as doing many other specialized tasks.
Each mitochondrion has a chromosome that is made of DNA (mitochondrial DNA or mtDNA) but is otherwise quite different from the better known chromosomes in the nucleus. The mitochondrial chromosome is much smaller. It is round (whereas the chromosomes in the nucleus are shaped like rods). There are many copies of the mitochondrial chromosome in every cell (whereas there is normally only one set of chromosomes in the nucleus). Mitochondrial DNA contains 37 genes which all are essential for normal function of the mitochondria. Many genetic conditions are related to changes in particular mitochondrial genes.