Introduction:-
Mendelian disorders are genetic abnormalities produced by mutations in a single gene. They are named after the father of genetics, Gregor Mendel. These diseases have four distinct inheritance patterns: X-linked dominant, X-linked recessive, autosomal dominant, and autosomal recessive. Mendel’s research on pea plants in the 19th century established the basis for our current understanding of how character are handed downward from parents to children in human genetics.
What Are Mendelian Disorders?
A single gene mutation can result in multiple health diseases known as Mendelian illnesses. Mendelian illnesses have relatively simple genetic roots, in compare to complex disorders, which are impacted by several genes and environmental variables. Depending on the kind of inheritance pattern, the mutation causing the condition may come from one or both parents.
Types of Mendelian Inheritance
1. Autosomal Dominant Inheritance: In autosomal dominant inheritance, the condition can be caused by a single copy of the defective gene, from either parent. This indicates that there is a 50% possibility that an offspring of a parent with a mutant gene will also have the condition. Autosomal dominant disorders: neurofibromatosis, Marfan syndrome, and Huntington’s disease are a few well-known examples.
These illnesses frequently have a distinct family history and impact several generations at a time. Even among family members who have the same mutation, the intensity and symptoms can differ greatly
2. Autosomal Recessive Inheritance: For a condition to appear, a mutation in one or both copies of the gene is required. This implies that the condition must either be inherited from both parents or both parents must be carriers of the mutation (having one copy of the mutant gene). There is a 25% risk that the child will be afflicted, a 50% probability that the child will be a carrier, and a 25% chance that the child will not be impacted if both parents are carriers.
Tay-Sachs disease, sickle cell anemia, and cystic fibrosis are a few examples of autosomal recessive illnesses. Because carriers usually don’t exhibit symptoms, these problems frequently arise in families where the disorder has never been diagnosed before.
3. X-Linked Dominant Inheritance: Gene mutations on the X chromosome are the source of X-linked dominant diseases. The X chromosome is divided into two in females and one in males, so the inheritance patterns are different in the sexes. Regardless of the child’s sex, a female with an X-linked dominant condition has a 50% probability of passing on the defective gene to her progeny. All of a male’s daughters will inherit the mutation from him, but none of his sons will.
Males are more likely to have more severe cases of these illnesses since they only have one X chromosome. Rett syndrome and X-linked hypophosphatemia are two examples.
