Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in living organisms.

Merlob Grunebaum Reisner Syndrome

Familial opposable triphalangeal thumbs duplication: A rare birth malformation where the thumb has three bones instead of the normal two which gives it a fingerlike appearance. An extra toe is also present.  ... read more »

What is a Cell?

Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions. ... read more »

Jewish Genetic Disorder: Mucolipidosis IV

Mucolipidosis IV is a rare genetic disorder passed down from parents to children. Both parents must carry the recessive gene for children to be affected. About 95% of people with Mucolipidosis IV have the typical or severe strain. ... read more »

Torsion Dystonia

Torsion Dystonia is a progressive genetic disorder that causes painful and debilitating muscle contractions. The most common form of the disease is early-onset with symptoms appearing in childhood. ... read more »

Canavan Disease

Canavan Disease is a genetic disorder commonly found in Ashkenazi Jews. The disease causes a premature breakdown of white matter in the brain. The disease is associated with chromosome 17. ... read more »

Fabry Disease

Fabry Disease is a genetic disorder passed along to children from the mother. The gene for the disorder is carried on the X chromosome. ... read more »

Familial Mediterranean Fever

Familial Mediterranean Fever (FMF) is a genetic disorder passed down from parents to children. The disease causes high fevers and bouts of inflammation. ... read more »

Fanconi Anemia

Fanconi Anemia is a genetic disorder that affects the bone marrow'sability to produce new or healthy red blood cells. Both parents mustcarry the affected gene to pass the disorder onto their children. ... read more »

Neiman Pick Disease

Neiman Pick disease is a group of genetic diseases. There are five types of the disease, types A, B, C, D and E. Each type of Neiman Pick affects different organs, but all affect cholesterol storage, fat storage or both. ... read more »

Lipoamide Dehydrogenase Deficiency

Lipoamide Dehydrogenase Deficiency is an extremely rare disease often referred to as E3. The condition is inherited. Due to the extreme rarity of the condition, significant medical information and treatment options are lacking. ... read more »

Maple Syrup Urine Disease

Maple Syrup Urine Disease is a genetic disorder. The most noticeable symptom of the condition is sweet scented urine that may smell similar to maple syrup. The disease prevents the body from breaking down amino acids effectively. ... read more »

Nemaline Myopathy

Nemaline Myopathy is a non-progressive neuromuscular disease that affects muscle strength and development. This condition is one of the 40 diseases currently covered by the MDA (Muscular Dystrophy Association). ... read more »

Usher Syndrome

Usher Syndrome is a relatively common genetic disorder that primarily affects vision and hearing. In some cases, children with a severe form of the disorder are born with substantial balance problems that affect motor coordination. ... read more »

What is a Gene?

A gene is the basic physical and functional unit of heredity. Genes, which are made up of DNA, act as instructions to make molecules called proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. ... read more »

What is a Chromosome?

In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure. ... read more »

How Many Chromosomes do People Have?

In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females. ... read more »

What are Proteins and What Do They Do?

Proteins are large, complex molecules that play many critical roles inthe body. They do most of the work in cells and are required for thestructure, function, and regulation of the body's tissues and organs. ... read more »

What is DNA?

DNA, or deoxyribonucleic acid, is the hereditary material in humans andalmost all other organisms. Nearly every cell in a person's body has the same DNA. Most DNA is located in the cell nucleus (where it is callednuclear DNA). ... read more »

What is Mitochondrial DNA?

Although most DNA is packaged in chromosomes within the nucleus, mitochondria also have a small amount of their own DNA. This genetic material is known as mitochondrial DNA or mtDNA. ... read more »

Can Genes be Turned On and Off in Cells?

Each cell expresses, or turns on, only a fraction of its genes. The rest of the genes are repressed, or turned off. The process of turning genes on and off is known as gene regulation. Gene regulation is an important part of normal development. ... read more »

What is the Epigenome?

DNA modifications that do not change the DNA sequence can affect gene activity. Chemical compounds that are added to single genes can regulate their activity; these modifications are known as epigenetic changes. ... read more »

How do Cells Divide?

There are two types of cell division: mitosis and meiosis. Most of thetime when people refer to 'cell division,' they mean mitosis, theprocess of making new body cells. Meiosis is the type of cell divisionthat creates egg and sperm cells. ... read more »

How do Genes Control the Growth and Division of Cells

A variety of genes are involved in the control of cell growth anddivision. The cell cycle is the cell's way of replicating itself in anorganized, step-by-step fashion. ... read more »

How Genes Work

How Genes Work ... read more »

How do Geneticists Indicate the Location of a Gene?

Geneticists use maps to describe the location of a particular geneon a chromosome. One type of map uses the cytogenetic location todescribe a gene's position. ... read more »

What are Gene Families?

A gene family is a group of genes that share important characteristics. In many cases, genes in a family share a similar sequence of DNA building blocks (nucleotides). ... read more »

How Can Gene Mutations Affect Health and Development

To function correctly, each cell depends on thousands of proteins to do their jobs in the right places at the right times. Sometimes, gene mutations prevent one or more of these proteins from working properly. ... read more »

Do All Gene Mutations Affect Health and Development?

No; only a small percentage of mutations cause genetic disorders'mosthave no impact on health or development. For example, some mutationsalter a gene's DNA sequence but do not change the function of theprotein made by the gene. ... read more »

Will Health Insurance Cover the Costs of Genetic Testing?

In many cases, health insurance plans will cover the costs ofgenetic testing when it is recommended by a person's doctor. Healthinsurance providers have different policies about which tests arecovered, however. ... read more »

Why is it Important to Know My Family Medical History?

A family medical history is a record of health information about a person and his or her close relatives. A complete record includes information from three generations of relatives. ... read more »

What are Reduced Penetrance and Variable Expressivity?

Reduced penetrance and variable expressivity are factors that influence the effects of particular genetic changes. These factors usually affect disorders that have an autosomal dominant pattern of inheritance. ... read more »

What do Geneticists Mean by Anticipation?

The signs and symptoms of some genetic conditions tend to become more severe and appear at an earlier age as the disorder is passed from one generation to the next. This phenomenon is called anticipation. ... read more »

What are Genomic Imprinting and Uniparental Disomy?

Genomic imprinting and uniparental disomy are factors that influence how some genetic conditions are inherited. ... read more »

Are Chromosomal Disorders Inherited?

Although it is possible to inherit some types of chromosomal abnormalities, most chromosomal disorders (such as Down syndrome and Turner syndrome) are not passed from one generation to the next. ... read more »

What is a Genetic Consultation?

A genetic consultation is a health service that provides information and support to people who have, or may be at risk for, genetic disorders. ... read more »

Why Might Someone Have a Genetic Consultation?

Individuals or families who are concerned about an inherited condition may benefit from a genetic consultation. The reasons that a person might be referred to a genetic counselor, medical geneticist, or other genetics professional include: ... read more »

What Happens During a Genetic Consultation?

A genetic consultation provides information, offers support, andaddresses a patient's specific questions and concerns. To help determine whether a condition has a genetic component, a genetics professionalasks about a person's medical history. ... read more »

How Can I Find a Genetics Professional in My Area?

To find a genetics professional in your community, you may wish to ask your doctor for a referral. If you have health insurance, you can also contact your insurance company to find a medical geneticist or genetic counselor in your area who participates in your plan. ... read more »

How are Genetic Conditions Diagnosed?

A doctor may suspect a diagnosis of a genetic condition on the basis of a person's physical characteristics and family history, or on theresults of a screening test. ... read more »

Mutations and Health

Mutations and Health ... read more »

How are Genetic Conditions Treated or Managed?

Many genetic disorders result from gene changes that are present in essentially every cell in the body. As a result, these disorders often affect many body systems, and most cannot be cured. ... read more »

What is Genetic Testing?

Genetic testing is a type of medical test that identifies changes in chromosomes, genes, or proteins. ... read more »

Genetic Consultation

Genetic Consultation ... read more »

How is Genetic Testing Done?

Once a person decides to proceed with genetic testing, a medical geneticist, primary care doctor, specialist, or nurse practitioner can order the test. Genetic testing is often done as part of a genetic consultation. ... read more »

What Kinds of Gene Mutations are Possible?

The DNA sequence of a gene can be altered in a number of ways. Gene mutations have varying effects on health, depending on where they occur and whether they alter the function of essential proteins. ... read more »

What is Direct-to-Consumer Genetic Testing?

Traditionally, genetic tests have been available only through healthcare providers such as physicians, nurse practitioners, and genetic counselors. ... read more »

What are Complex or Multifactorial Disorders?

Researchers are learning that nearly all conditions and diseases have a genetic component. Some disorders, such as sickle cell anemia and cystic fibrosis, are caused by mutations in a single gene. ... read more »

How Can Consumers be Sure a Genetic Test is Valid and Useful?

Before undergoing genetic testing, it is important to be sure that the test is valid and useful. A genetic test is valid if it provides an accurate result. Two main measures of accuracy apply to genetic tests: analytical validity and clinical validity. ... read more »

How are Genetic Conditions and Genes Named?

Genetic conditions are not named in one standard way (unlike genes, which are given an official name and symbol by a formal committee). Doctors who treat families with a particular disorder are often the first to propose a name for the condition. ... read more »

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