Genetic disorders

A genetic disorder is a condition that is caused by an abnormality in an individual's DNA. Abnormalities can be as small as a single-base mutation in just one gene, or they can involve the addition or subtraction of entire chromosomes. To learn more about the different types of genetic disorders and see some specific examples, browse through the pages below.

cdascher / Getty Images Patterns of Inheritance The various patterns of inheritance are attributed to Austrian scientist Gregor Mendel, who discovered them while working with garden pea hybrids in the 1800s. Mendel sometimes is referred to as the father of modern genetics; likewise, the patterns of inheritance for single-gene diseases are often described as Mendelian. Two primary factors influence the likelihood a person will inherit a genetic disorder: • Whether one copy of the mutated gene (from either parent) is passed down or whether two copies (one from both parents) are passed down • Whether the mutation is on one of the sex chromosomes (X or Y) or on one of 22 other pairs of non-sex chromosomes (called autosomes) Dominant and Recessive Genes A genetic mutation is a change In a genetic code. However, a female with a genetic mutation on one X chromosome is a carrier of that disorder. From a statistical standpoint, this means 50% of her sons will inherit the mutation and develop the disorder, while 50% of her daughters will inherit the mutation and become a carrier. Examples of X-linked recessive disorders are hemophilia and Y-Linked Disorders Because only males have a Y chromosome, only males can be affected by and pass on Y-linked disorders. All sons of a man with a Y-linked disorder will inherit the condition from their father. Some examples of Y-linked disorders are Y chromosome infertility and cases of Swyer syndrome in which a male's testicles do not develop norm...

The genetic basis of Down syndrome There are 23 pairs of chromosomes, for a total of 46. Half the chromosomes come from the egg (the mother) and half come from the sperm (the father). This XY chromosome pair includes the X chromosome from the egg and the Y chromosome from the sperm. In Down syndrome, there is an additional copy of chromosome 21, resulting in three copies instead of the normal two copies. Down syndrome is a genetic disorder caused when abnormal cell division results in an extra full or partial copy of chromosome 21. This extra genetic material causes the developmental changes and physical features of Down syndrome. Down syndrome varies in severity among individuals, causing lifelong intellectual disability and developmental delays. It's the most common genetic chromosomal disorder and cause of learning disabilities in children. It also commonly causes other medical abnormalities, including heart and gastrointestinal disorders. Symptoms Each person with Down syndrome is an individual — intellectual and developmental problems may be mild, moderate or severe. Some people are healthy while others have significant health problems such as serious heart defects. Children and adults with Down syndrome have distinct facial features. Though not all people with Down syndrome have the same features, some of the more common features include: • Flattened face • Small head • Short neck • Protruding tongue • Upward slanting eye lids (palpebral fissures) • Unusually shaped ...

Overview Ehlers-Danlos syndrome is a group of inherited disorders that affect your connective tissues — primarily your skin, joints and blood vessel walls. Connective tissue is a complex mixture of proteins and other substances that provide strength and elasticity to the underlying structures in your body. People who have Ehlers-Danlos syndrome usually have overly flexible joints and stretchy, fragile skin. This can become a problem if you have a wound that requires stitches, because the skin often isn't strong enough to hold them. A more severe form of the disorder, called vascular Ehlers-Danlos syndrome, can cause the walls of your blood vessels, intestines or uterus to rupture. Because vascular Ehlers-Danlos syndrome can have serious potential complications in pregnancy, you may want to talk to a genetic counselor before starting a family. Symptoms There are many different types of Ehlers-Danlos syndrome, but the most common signs and symptoms include: • Overly flexible joints. Because the connective tissue that holds joints together is looser, your joints can move far past the normal range of motion. Joint pain and dislocations are common. • Stretchy skin. Weakened connective tissue allows your skin to stretch much more than usual. You may be able to pull a pinch of skin up away from your flesh, but it will snap right back into place when you let go. Your skin might also feel exceptionally soft and velvety. • Fragile skin. Damaged skin often doesn't heal well. For exam...

An autosomal dominant disorder is caused by just one faulty gene from either parent. “Autosomal” means that the defective gene is located on any of the chromosomes that are not the sex chromosomes (X or Y). If one parent has the gene, each child of the couple has a 50 percent chance of inheriting the disorder. An example of an autosomal dominant disorder is • What is an autosomal recessive disorder? A If both parents are carriers of an abnormal gene, there is a 25 percent chance that the child will get the abnormal gene from each parent and will have the disorder. There is a 50 percent chance that the child will be a carrier of the disorder—just like the carrier parents. If only one parent is a carrier, there is a 50 percent chance that the child will be a carrier. • What are sex-linked disorders? Most babies with genetic disorders are born to couples without risk factors. But the risk of genetic disorders is higher when certain factors are present. This is why screening begins by assessing your risk factors before or during pregnancy. You are at increased risk if • you have a genetic disorder • you have a child with a genetic disorder • there is a family history of a genetic disorder Some genetic disorders are more common in certain ethnic groups. • What is genetic counseling? Diagnostic tests may be recommended if a screening test shows an increased risk of a birth defect. Diagnostic tests should also be offered as a first choice to everyone during pregnancy, even if you...

Genetic Disorders Genetic disorders are due to alterations or abnormalities in the genome of an organism. A genetic disorder may be caused by a mutation in a single gene or multiple genes. It can also be due to changes in the number or structure of chromosomes. Genes are the basic unit of heredity. They hold the genetic information in the form of DNA which can be translated into useful proteins to carry out life processes. These genes undergo a mutation sometimes, which changes the instructions to formulate the protein, due to which the protein does not work properly. Such disorders are known as genetic disorders. Some genetic disorders are innate, i.e., present by birth, while others are acquired due to mutations in a particular gene. The genetic disorders that are present by birth are inherited from parents, e.g. cystic fibrosis, haemophilia, sickle cell anaemia, etc. The genetic disorders that are acquired during the lifetime are not inherited from parents, these occur due to mutations that occur randomly or due to exposure to certain chemicals, environments or radiations such as cigarette smoke, UV radiations, etc. Cancer is one such disease. The genetic disorders can be categorized into two types, namely Let us explore genetic disorder notes to know about the different types of genetic disorders. Types of Genetic Disorders Mendelian Disorder • These disorders occur due to mutations in a single gene and can be easily detected by pedigree analysis. • These disorders can...

Genetic disorders is a category of diseases that includes certain types of birth defects, chronic diseases, developmental problems, and sensory deficits that are inherited from one or both parents. Birth defects • • • • contractures • • genital malformations • • misshapen skull • missing fingers or toes • missing or incomplete arms or legs • Chronic diseases • bleeding disorders • childhood • kidney or urinary tract disease • slow growth or short stature • • • Developmental problems • • • • • • loss of developmental skills • • mental illness • mental retardation • speech problems • Sensory deficits • • • • Some of the symptoms can be the same as those for conditions that are not inherited. Features can appear at birth (congenital heart disease, or cleft lip or palate) or during the course of childhood (developmental delays or learning problems). Diagnosis may involve a physical exam or targeted What are the physical signs of genetic disorders? The following list includes features that might suggest that your child has a genetic disorder. However, some of these characteristics are commonly found in people without a disorder. You'll want to check with your doctor if your child has at least two of the following features: • ear abnormalities • unusually shaped eyes • different colored eyes • facial features that are unusual or different from other family members • brittle or sparse hair • excessive body hair • white patches of hair • large or small tongue • misshapen teeth • m...