Mendelian disorders are a form of genetic disorder that develops as a result of changes in one gene or anomalies in the genome. A disorder like this can be seen from birth and discovered through family lineage and the genealogical record. The family examination is the name given to the investigation that is done to investigate these disorders.
These inherited disorders are extremely rare, affecting only one person in a thousand or one million. Hereditary problems, on the other hand, can be acquired. Non-inheritable hereditary problems are caused, for the most part, by mutations or errors in the DNA. Inheritable hereditary difficulties, on the other hand, usually occur in the germline cells.
Principles of Mendelian Disorders
Mendel’s research on pea plants in terms of inheritance patterns has provided a solid foundation for our understanding of single-gene diseases in humans. Mendelian Disorder is caused by mutations in a single gene. Mendelian disorders are caused by single-locus mutations.
This might happen on the autosome or the sex chromosome. Pedigree’s study of a family with a history of Mendelian disorder can be used to determine whether the trait is dominant or recessive and the likelihood of reappearance in future generations.
Types of Mendelian Disorders
The different types of Mendelian Disorders are Autosomal dominant, Autosomal recessive, Sex-linked dominant, Sex-linked recessive, and Mitochondrial disorders.
Common Mendelian Disorders
Some of the common Mendelian disorders are Thalassemia, Haemophilia, Muscular Dystrophy, Sickle cell anemia, Cystic fibrosis, Phenylketonuria, Colour blindness, and Skeletal dysplasia disorder.
Thalassemia
- This is a genetic condition in which the body does not produce enough hemoglobin. As a result, a large number of red blood cells are destroyed, resulting in anemia in patients. Fatigue, weakness, and paleness are all symptoms of thalassemia
- It is a recessive autosomal condition. minor, intermedia, and major thalassemia are the three forms of thalassemia determined on severity
- People who’ve thalassemia minor bring the genetic trait for thalassemia however do not normally enjoy any fitness issues besides possibly a slight anemia
- Thalassemia intermedia is a time period used to explain a set of sufferers with β thalassemia in whom the medical severity of the disorder is someplace among the moderate signs and symptoms of the β thalassemia trait and the excessive manifestations of β thalassemia major
- Thalassemia major is the maximum extreme form of beta thalassemia. It develops where beta globin genes are missing. The signs and symptoms of thalassemia major normally seem earlier than a child’s second birthday
- This form of thalassemia is generally so extreme that it requires everyday blood transfusions
- Thalassemia causes facial bone deformations, swelling in the abdomen, and black urine, among other symptoms and effects
- Because thalassemia is caused by a single allele mutation in the HBA1 and HBA2 genes, which are inherited in a Mendelian recessive way, it is a Mendelian condition
- Thalassaemia patients have lower levels of hemoglobin and circulating red blood cells than healthy people, resulting in mild to severe anemia. Cause: Though not always the case, autosomal recessive inheritance is common in both and -thalassemias
- Thalassemias are a group of Mendelian diseases caused by abnormalities in the manufacturing of globin polypeptides. The absence or reduced synthesis of one of the globin chains results in an excess of that chain. As a result, a large number of red blood cells are damaged, resulting in anaemia
- Some babies are born with thalassemia symptoms, while others develop them during their first two years of life. Thalassemia symptoms are not always present in patients who simply have one defective haemoglobin gene
- Hemoglobin molecules are made up of alpha and beta chains, which are susceptible to mutations. The production of either the alpha or beta chains is diminished in thalassemia, resulting in alpha- or beta-thalassemia
- The severity of alpha-thalassemia is determined by the number of gene mutations you receive from your parents. The more mutated genes you have, the worse your thalassemia will be
- The severity of beta-thalassemia is determined by the section of the hemoglobin molecule that is damaged
Risk Factors
The following factors can raise your risk of thalassemia:
- Thalassemia runs in the family. Thalassemia is handed down the generations due to faulty hemoglobin genes
- Ancestry can be traced back to a certain ancestor. African Americans, as well as those of Mediterranean and Southeast Asian origin, are more likely to develop thalassemia
Complications
The following are some of the possible side effects of moderate to severe thalassemia:
- An overabundance of iron: People with thalassemia can accumulate an excessive amount of iron in their systems as a result of the disease or frequent blood transfusions. Too much iron can harm your heart, liver, and endocrine system, which includes hormone-producing glands that control your body’s activities
- Infection: Infection is more likely in those with thalassemia. This is particularly true if your spleen has been removed
Haemophilia
- This is a form of the recessive sex-linked disorder. According to the genetic pattern, the hemophilic features are passed down to the son of an unaffected carrier mother
This X-linked genetic condition affects only a small percentage of females. For a daughter to be hemophilic, the mother must be a carrier or haemophilic, but the father must be haemophilic at all times.
Blood clotting problems are caused by haemophilia. The blood in these patients does not clot normally because the protein that aids in blood coagulation is defective. As a result, individuals suffering from this infection frequently experiences unexplained and excessive bleeding from cuts or wounds.
Because X-linked chromosome abnormalities create this type of genetic illness, males are disproportionately affected.
Sickle Cell anaemia
- This is an autosomal recessive hereditary condition
A sickle cell anaemic person normally inherits the faulty gene from both carrier parents, according to the Mendelian pattern of inheritance.
Changes in the location of the 6th amino acid in the beta-globin chain of haemoglobin cause Sickle Cell anemia. The amino acid Glutamate is replaced with Valine in this case.
A physical alteration in the mutant hemoglobin molecule triggers the transformation of a biconcave RBC into a Sickle Cell.
Because of its distorted shape, this sickle-celled RBC has a reduced oxygen-carrying capacity than biconcave RBCs.
Conclusion
Mendelian disorder is a form of genetic disorder that is caused by mutations in a single gene or anomalies in the genome. Such a disorder can be detected from birth and derived from family history through the use of a family tree. Pedigree analysis is the term for the analysis that is carried out as a result of this.