All About Human Genetic Disorders

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Hemophilia: The Blood Clotting Disease

Most famous for its appearance in several European royal families, hemophilia is the most well-known of the blood clotting disorders. Mutations in genes called F8 and F9 lead to abnormal blood clotting and an increased risk of serious hemorrhaging.

The PT Gene Mutation

The gene known as F2 codes for the protein prothrombin, a protein coagulation factor that plays an essential role in blood clotting. Mutations in this gene are known as PT gene mutations, and result in increased risk of stroke, heart attack, thrombosis, and embolism.

The Genetics of Factor V Leiden Thrombophilia

Another type of clotting disorder, factor V Leiden thrombophilia, is caused by a mutation in the F5 gene which codes for a clotting protein called coagulation factor V. Normally this protein slows down the clotting process and helps reduce clot size. Abnormal versions of the protein lead to increased risk of thrombosis, embolism, and miscarriage.

Transmission and Detection of Hypertrophic Cardiomyopathy Mutations

Hypertrophic cardiomyopathy is a type of heart disease that causes the heart muscle to become thicker than normal. This can lead to faulty valve action and obstruction of blood flow, and bring about early death by heart attack. The underlying genetic causes are mutations in a collection of genes known as HCM genes.

Short Stature Disorders caused by SHOX Gene Mutation

The SHOX gene is essential for correct regulation of human development and growth; mutations in this gene are responsible for several different short stature disorders. Two of these are Turner syndrome and Leri-Weill dyschondrosteosis. In each of these disorders, SHOX gene mutations lead to dysfunctional skeletal growth.

The Genetics of Achondroplastic Dwarfism

Achrondroplastic dwarfism is perhaps the most well-known of the short stature disorders. A characteristic feature is short-limbs, the result of a mutation in a gene called FGFR3. The mutated gene leads to abnormal maintenance of bone tissue, especially of the long bones of the legs and arms.

The Genetics of Psoriasis

While psoriasis is an autoimmune disease triggered when the immune system begins to attack proteins in skin cells, the underlying cause is genetic in nature. Several genes which play a role in the development of psoriasis have been identified, including PSORS1, LCE3B and LCE3C.

Genetic Influences on the Development of Melanoma

The development of melanoma skin cancer is complex, and is heavily influenced by genetics as well as by UV exposure and sun-related skin damage. Several genes have been identified as having an influence on the development of this cancer.

An Overview of Xeroderma Pigmentosum

People with this genetic disorder are extremely sensitive to sunlight and severe sun damage, and therefore are at increased risk of skin and eye cancers. At least nine genes have been implicated in xeroderma pigmentosum, with a mutation in any one of them leading to increased risk of developing the disorder.

The Link between BRAF Gene Mutations and Cancer

The BRAF gene codes for a protein called serine/threonine protein kinase, a type of enzyme involved in cell division and differentiation. Mutations in this gene are associated with an increased risk of several cancers, including lung, colon, and thyroid cancer, melanoma, and non-Hodgkin’s lymphoma.

Genetic Mutations and Colon Disorders

Mutations in several different genes can lead to an increased risk of colon cancer and familial colon disorders such as hereditary nonpolyposis colorectal cancer and Peutz-Jeghers syndrome. In most cases, these genetic mutations cause one or more colon disorders that increase the risk of cancer developing.

Cystic Fibrosis and the CFTR Gene

In the US, cystic fibrosis is one of the most common causes of infant mortality. The disease is caused by mutations in the CFTR gene, which codes for a type of protein that transports molecules within cells. Mutations in this gene lead to abnormal chloride trafficking across cell membranes, causing the formation of sticky, thick mucus that clogs the lungs.

A Guide to Aicardi Syndrome

Aircardi syndrome is an X-linked disorder that affects newborn girls. Girls born with the syndrome have structural brain abnormalities and retinal lesions, and are at risk of seizures. With fewer than 1,000 reported cases in the US and only around 4,000 worldwide, many of the details of this rare condition are still a mystery.

Bloom’s Syndrome and Tay-Sach’s Disease

These two conditions are both very rare in the general population, but are much more common among Ashkenazi Jews. The cause of Bloom’s syndrome is a mutation in a gene called BLM, which is involved in DNA replication. In the case of Tay-Sach’s disease, the relevant gene codes for a protein called hexosaminidase A. When the gene is mutated, the protein is non-functional and accumulates in the brain, causing progressive destruction of nerve cells.

Dystrophin Gene Mutations

Mutations in this gene can cause a number of muscular dystrophies, including Duchenne’s and Becker’s. The main feature of each of these diseases is progressive muscle wasting, eventually leading to death by respiratory or heart failure.

The Genetics of Lesch-Nyhan Syndrome

This genetic disorder affects how the body metabolizes purines, a component of DNA. Mutations in a gene called HPRT__1 affects the body’s levels of an enzyme called hypoxanthine guanine phosphoribosyltransferase, which in turn causes the build-up of uric acid, leading to the development of kidney and bladder stones.

Severe Congenital Neutropenia and Severe Combined Immunodeficiency

These genetic disorders affect the body’s immune system. In the case of severe congenital neutropenia, one of several different gene mutations lead to low levels of neutrophils, a type of immune cell involved in the first line of defense against disease. Severe combined immunodeficiency leads to an almost complete loss of immunity against all diseases.

One of the Rarest Genetic Disorders: Costello Syndrome

With only around 150 cases reported worldwide, Costello syndrome is one of the rarest known genetic disorders. The syndrome is caused by mutations in the HRAS gene, which leads to continual production of H-Ras protein. Accumulation of the protein creates a wide variety of symptoms, including developmental delay, short stature, and benign tumor growth.

Progeria: The Early-Onset Aging Disease

Progeria causes children to grow physically old at a highly accelerated rate. A single mutation in a gene called LMNA leads to the formation of abnormal and inactive Lamin A protein. Without a usable form of Lamin A, the body’s cells are unstable, and all of the body’s tissue types, including bone, muscle, and connective tissue, are affected.

Genes Affected in Huntington’s Disease

This degenerative brain disease develops due to mutations in the gene that codes for a protein called huntingtin. The genetics of Huntington’s disease are intriguing, as it is caused by repetition of a certain DNA sequence, rather than a mutation.

The Influence of Genetics on Idiopathic Epilepsy

For many people, epilepsy is a symptom of another disorder, or the cause of a traumatic brain injury. In some cases, however, the condition is idiopathic, which means there is no underlying cause, and genetics is likely to play a role.

Klippel-Feil Syndrome and the PAX Gene Family

This rare genetic disorder causes the fusion of neck vertebrae in a developing fetus, as well as structural abnormalities and organ defects. Genes in the PAX family are thought to be involved.

Combined Tuberous Sclerosis: Genetics and Testing

Tuberous sclerosis is a rare genetic disorder that causes the growth of tumors in many vital organs, including the brain. A mutation in either of two genes, TSC1 and TSC2, can cause this disorder. The large number of possible mutations, together with the involvement of two different genes, makes testing for this disorder quite complex.


  • This is a compilation of articles contained on the Bright Hub site. References and resources used by the authors to create each piece of content within the compilation can be found on the individual articles themselves.