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What Is Down Syndrome? - Symptoms, Causes & Facts

Instructor: John Williams

Down Syndrome is a genetic disease that does not follow the traditional method of inheritance. Most people are familiar with the basics of this disease, but know very little about the details of this syndrome and its effects in humans. In this lesson we'll learn about this disease, its symptoms, and its causes.

We also recommend watching What Is Huntington's Disease? - Symptoms, Genetic Cause & Treatment and Down Syndrome: Cause, Progression, and Treatment

Introduction

A number of diseases are genetic. This means that the source of these diseases lies in the inherited traits and genes received from the mother and the father of the individual. These diseases are often the result of dominant/recessive inheritance, such as with sickle-cell anemia and cystic fibrosis. However, in some cases, genetic diseases may be caused by issues in the process of meiosis, or sex cell production. This lesson will discuss one of these diseases: Down Syndrome.

Meiosis and Down Syndrome

The human genome has 23 pairs of chromosomes (condensed DNA). This means that we have 46 chromosomes that provide the genetic information needed to make us who we are. In order for reproduction to occur, these chromosomes have to be divided in half in the sperm and egg cells of the parents. During this process, the pairs of chromosomes split so that only one of each pair will make it into the sperm or egg cell. When the egg and sperm cells unite, each pair is restored in the newly formed individual, and 23 pairs will now exist in the genome.

Occasionally, however, this separation does not take place properly. In the event that pairs are not separated, it is possible that a person may receive an inappropriate number of chromosomes, such as three, where there should be only a pair. This condition is known as trisomy, and is the presence of three chromosomes in the portion of the DNA that should only have two.

Down Syndrome

Down Syndrome is also called trisomy 21. This name means that the 21st pair of chromosomes contains an additional copy. In genetics, having more than the normal number is often a problem, and in this case, it can cause many physical and mental symptoms. While not all symptoms of Down Syndrome are not seen in all patients, several are relatively common.

Down Syndrome leads to stunted growth in the individual. This is seen in 100% of the cases that have been evaluated globally. Out of the many symptoms of this disease that exist, this one is the most common. Roughly 99% of the individuals with Down Syndrome will also demonstrate some mental development delays. It is important to note that a small number of individuals with Down Syndrome may be able to develop normal mental functions. Other common symptoms include weaker muscles, smaller genitalia, and small teeth. While this is not a complete list of symptoms for this disease, these represent some of the most common ones that are exhibited.

Karyotype of Trisomy 21
Trisomy 21

Treatment for Down Syndrome

While there is no cure for Down Syndrome, researchers have developed ways to treat and manage the symptoms and signs of this disease. Early educational intervention allows for many individuals afflicted with Down Syndrome to obtain education and work in a job setting. Occasionally, individuals with Down Syndrome may also attend college and receive higher educational and technical training. The key, however, is early intervention, meaning that professional help should be sought as soon as the child is born.

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