Monogenic Mendelian inheritance, also known as single-gene inheritance, is a type of inheritance pattern in which a trait or disorder is determined by a single gene. These genes are typically located on the autosomal chromosomes (the non-sex chromosomes), and can be inherited in a predictable manner according to the laws of Mendelian genetics.
Mendelian genetics describes how traits are passed down from one generation to the next through the inheritance of genes from parents. There are three main types of Mendelian inheritance: autosomal dominant, autosomal recessive, and X-linked inheritance.
In autosomal dominant inheritance, an individual only needs to inherit one copy of the dominant gene from one parent to express the trait or disorder. The gene is expressed even if only one copy is present in the individual’s genome. For example, Huntington’s disease is a rare neurodegenerative disorder that is caused by a single dominant gene.
In autosomal recessive inheritance, an individual needs to inherit two copies of the recessive gene (one from each parent) to express the trait or disorder. The gene is only expressed if both copies are present. Examples of recessive disorders include sickle cell anemia and cystic fibrosis.
In X-linked inheritance, the gene is located on the X chromosome. Males have one X chromosome and one Y chromosome, while females have two X chromosomes. Because males have only one X chromosome, they are more likely to express a disorder caused by a recessive gene on the X chromosome. Examples of X-linked disorders include hemophilia and color blindness.
In summary, monogenic Mendelian inheritance refers to the inheritance of a trait or disorder that is determined by a single gene. The pattern of inheritance can be autosomal dominant, autosomal recessive, or X-linked, and can be predicted using the laws of Mendelian genetics.