Autosomal dominant in the context of Y-linked


Autosomal dominant in the context of Y-linked

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⭐ Core Definition: Autosomal dominant

In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and the second is called recessive. This state of having two different variants of the same gene on each chromosome is originally caused by a mutation in one of the genes, either new (de novo) or inherited. The terms autosomal dominant or autosomal recessive are used to describe gene variants on non-sex chromosomes (autosomes) and their associated traits, while those on sex chromosomes (allosomes) are termed X-linked dominant, X-linked recessive or Y-linked; these have an inheritance and presentation pattern that depends on the sex of both the parent and the child (see Sex linkage). Since there is only one Y chromosome, Y-linked traits cannot be dominant or recessive. Additionally, there are other forms of dominance, such as incomplete dominance, in which a gene variant has a partial effect compared to when it is present on both chromosomes, and co-dominance, in which different variants on each chromosome both show their associated traits.

Dominance is a key concept in Mendelian inheritance and classical genetics. Letters and Punnett squares are used to demonstrate the principles of dominance in teaching, and the upper-case letters are used to denote dominant alleles and lower-case letters are used for recessive alleles. An often quoted example of dominance is the inheritance of seed shape in peas. Peas may be round, associated with allele R, or wrinkled, associated with allele r. In this case, three combinations of alleles (genotypes) are possible: RR, Rr, and rr. The RR (homozygous) individuals have round peas, and the rr (homozygous) individuals have wrinkled peas. In Rr (heterozygous) individuals, the R allele masks the presence of the r allele, so these individuals also have round peas. Thus, allele R is dominant over allele r, and allele r is recessive to allele R.

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Autosomal dominant in the context of Genetic disorder

A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality. Although polygenic disorders are the most common, the term is mostly used when discussing disorders with a single genetic cause, either in a gene or chromosome. The mutation responsible can occur spontaneously before embryonic development (a de novo mutation), or it can be inherited from two parents who are carriers of a faulty gene (autosomal recessive inheritance) or from a parent with the disorder (autosomal dominant inheritance). When the genetic disorder is inherited from one or both parents, it is also classified as a hereditary disease. Some disorders are caused by a mutation on the X chromosome and have X-linked inheritance. Very few disorders are inherited on the Y chromosome or mitochondrial DNA (due to their size).

There are well over 6,000 known genetic disorders, and new genetic disorders are constantly being described in medical literature. More than 600 genetic disorders are treatable. Around 1 in 50 people are affected by a known single-gene disorder, while around 1 in 263 are affected by a chromosomal disorder. Around 65% of people have some kind of health problem as a result of congenital genetic mutations. Due to the significantly large number of genetic disorders, approximately 1 in 21 people are affected by a genetic disorder classified as "rare" (usually defined as affecting less than 1 in 2,000 people). Most genetic disorders are rare in themselves.

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Autosomal dominant in the context of Photic sneeze reflex

The photic sneeze reflex (also known as ACHOO syndrome, a contrived acronym for Autosomal-dominant Compelling Helio-Ophthalmic Outburst) is an inherited and congenital autosomal dominant reflex condition that causes sneezing in response to numerous stimuli, such as looking at bright lights or periocular (surrounding the eyeball) injection. The condition affects 18 to 35% of the world's population, but its exact mechanism of action is not well understood.

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Autosomal dominant in the context of Snatiation

Snatiation is a term coined to refer to the medical condition originally termed "stomach sneeze reflex", which is characterized by uncontrollable bursts of sneezing brought on by fullness of the stomach, typically immediately after a large meal. The type of food consumed does not appear to affect its occurrence. It is reported, based on a preliminary study, to be passed along genetically as an autosomal dominant trait, as first described by Ahmad Teebi and Qasem Al-Saleh in 1989. The term "snatiation", coined shortly thereafter in a humorous letter to the Journal of Medical Genetics by Judith G. Hall, is a portmanteau of the words sneeze and satiation. Similar in nature to this condition is gustatory rhinitis, which involves rhinorrhea induced by certain foods, such as spicy foods.

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Autosomal dominant in the context of Maturity-onset diabetes of the young

Maturity-onset diabetes of the young (MODY) refers to any of several hereditary forms of diabetes mellitus caused by mutations in an autosomal dominant gene disrupting insulin production. Along with neonatal diabetes, MODY is a form of the conditions known as monogenic diabetes. While the more common types of diabetes (especially type 1 and type 2) involve more complex combinations of causes involving multiple genes and environmental factors, each form of MODY is caused by changes to a single gene (monogenic). HNF1A-MODY (MODY 3) are the most common forms.

Robert Tattersall and Stefan Fajans initially identified the phenomenon known as maturity onset diabetes of the young in a classic study published in the journal Diabetes in 1975.

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Autosomal dominant in the context of Andersen–Tawil syndrome

Andersen–Tawil syndrome, also called Andersen syndrome and long QT syndrome 7, is a rare genetic disorder affecting several parts of the body. The three predominant features of Andersen–Tawil syndrome include disturbances of the electrical function of the heart characterised by an abnormality seen on an electrocardiogram (a long QT interval) and a tendency to abnormal heart rhythms, physical characteristics including low-set ears and a small lower jaw, and intermittent periods of muscle weakness known as hypokalaemic periodic paralysis.

Andersen–Tawil syndrome is inherited in an autosomal dominant pattern. It is caused in most cases by a mutation in the KCNJ2 gene which encodes an ion channel that transports potassium out of cardiac muscle cells. The arrhythmias seen in the condition can be treated with flecainide or beta-blockers, but an implantable defibrillator may sometimes be required. Periodic paralysis can be treated with carbonic anhydrase inhibitors such as acetazolamide. The condition is very rare and is estimated to affect one person in every million. The three groups of features seen in this condition were first described in 1971 by Ellen Andersen, and significant contributions to its understanding were made by Rabi Tawil.

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Autosomal dominant in the context of Porphyria

Porphyria (/pɔːrˈfɪriə/ or /pɔːrˈfriə/) is a group of disorders in which substances called porphyrins build up in the body, adversely affecting the skin or nervous system. The types that affect the nervous system are also known as acute porphyria, as symptoms are rapid in onset and short in duration. Symptoms of an attack include abdominal pain, chest pain, vomiting, confusion, constipation, fever, high blood pressure, and high heart rate. The attacks usually last for days to weeks. Complications may include paralysis, low blood sodium levels, and seizures. Attacks may be triggered by alcohol, smoking, hormonal changes, fasting, stress, or certain medications. If the skin is affected, blisters or itching may occur with sunlight exposure.

Most types of porphyria are inherited from one or both of a person's parents and are due to a mutation in one of the genes that make heme. They may be inherited in an autosomal dominant, autosomal recessive, or X-linked dominant manner. One type, porphyria cutanea tarda, may also be due to hemochromatosis (increased iron in the liver), hepatitis C, alcohol, or HIV/AIDS. The underlying mechanism results in a decrease in the amount of heme produced and a build-up of substances involved in making heme. Porphyrias may also be classified by whether the liver or bone marrow is affected. Diagnosis is typically made by blood, urine, and stool tests. Genetic testing may be done to determine the specific mutation. Hepatic porphyrias are those in which the enzyme deficiency occurs in the liver. Hepatic porphyrias include acute intermittent porphyria (AIP), variegate porphyria (VP), aminolevulinic acid dehydratase deficiency porphyria (ALAD), hereditary coproporphyria (HCP), and porphyria cutanea tarda.

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Autosomal dominant in the context of Osteogenesis imperfecta

Osteogenesis imperfecta (IPA: /ˌɒstiˈɛnəsɪs ˌɪmpɜːrˈfɛktə/; OI), colloquially known as brittle bone disease, is a group of genetic disorders that all result in bones that break easily. The range of symptoms—on the skeleton as well as on the body's other organs—may be mild to severe. Symptoms found in various types of OI include whites of the eye (sclerae) that are blue instead, short stature, loose joints, hearing loss, breathing problems and problems with the teeth (dentinogenesis imperfecta). Potentially life-threatening complications, all of which become more common in more severe OI, include: tearing (dissection) of the major arteries, such as the aorta; pulmonary valve insufficiency secondary to distortion of the ribcage; and basilar invagination.

The underlying mechanism is usually a problem with connective tissue due to a lack of, or poorly formed, type I collagen. In more than 90% of cases, OI occurs due to mutations in the COL1A1 or COL1A2 genes. These mutations may be hereditary in an autosomal dominant manner but may also occur spontaneously (de novo). There are four clinically defined types: type I, the least severe; type IV, moderately severe; type III, severe and progressively deforming; and type II, perinatally lethal. As of September 2021, 19 different genes are known to cause the 21 documented genetically defined types of OI, many of which are extremely rare and have only been documented in a few individuals. Diagnosis is often based on symptoms and may be confirmed by collagen biopsy or DNA sequencing.

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Autosomal dominant in the context of Multiple endocrine neoplasia

Multiple endocrine neoplasia (abbreviated MEN) is a condition which encompasses several distinct syndromes featuring tumors of endocrine glands, each with its own characteristic pattern. In some cases, the tumors are malignant, in others, benign. Benign or malignant tumors of nonendocrine tissues occur as components of some of these tumor syndromes.

MEN syndromes are inherited as autosomal dominant disorders.

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Autosomal dominant in the context of Creutzfeldt–Jakob disease

Creutzfeldt–Jakob disease (CJD) is an incurable, invariably fatal, neurodegenerative disease belonging to the transmissible spongiform encephalopathy (TSE) group. Early symptoms include memory problems, behavioral changes, poor coordination, visual disturbances and auditory disturbances. Later symptoms include dementia, involuntary movements, blindness, deafness, weakness, and coma. About 70% of sufferers die within a year of diagnosis. The name "Creutzfeldt–Jakob disease" was introduced by Walther Spielmeyer in 1922, after the German neurologists Hans Gerhard Creutzfeldt and Alfons Maria Jakob.

CJD is caused by a prion, an infectious abnormal folding of a protein. Infectious prions are misfolded proteins that can cause normally folded proteins to also become misfolded. About 85% of cases of CJD occur for unknown reasons, while about 7.5% of cases are inherited in an autosomal dominant manner. Exposure to brain or spinal tissue from an infected person may also result in spread. There is no evidence that sporadic CJD can spread among people via normal contact or blood transfusions, although this is possible in variant Creutzfeldt–Jakob disease. Diagnosis involves ruling out other potential causes. An electroencephalogram, spinal tap, or magnetic resonance imaging may support the diagnosis. Another diagnosis technique is the real-time quaking-induced conversion assay, which can detect the disease in early stages.

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Autosomal dominant in the context of Carney complex

Carney complex and its subsets LAMB syndrome and NAME syndrome are autosomal dominant conditions comprising myxomas of the heart and skin, hyperpigmentation of the skin (lentiginosis), and endocrine overactivity. It is distinct from Carney triad. Approximately 7% of all cardiac myxomas are associated with Carney complex.

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Autosomal dominant in the context of Ehlers–Danlos syndromes

Ehlers–Danlos syndromes (EDS) are a group of 13 genetic connective tissue disorders. Symptoms often include loose joints, joint pain, stretchy, velvety skin, and abnormal scar formation. These may be noticed at birth or in early childhood. Complications may include aortic dissection, joint dislocations, scoliosis, chronic pain, or early osteoarthritis. The existing classification was last updated in 2017, when a number of rarer forms of EDS were added.

EDS occurs due to mutations in one or more particular genes—there are 19 genes that can contribute to the condition. The specific gene affected determines the type of EDS, though the genetic causes of hypermobile Ehlers–Danlos syndrome (hEDS) are still unknown. Some cases result from a new variation occurring during early development. In contrast, others are inherited in an autosomal dominant or recessive manner. Typically, these variations result in defects in the structure or processing of the protein collagen or tenascin.

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