Down+Syndrome

By, Stephen Ferraro

**How do you get down syndrome?**

Down syndrome is a genetic disease. Also it can be called Trisomy 21. It is caused by the presence of all or part of a 21st chromosome. It can be passed down through one of your parents. It is one of the most common genetic disease. Down syndrome occurs in one out of 700 to 800 infants. Down syndrome is caused by a person having three copies of chromosome 21 instead of two copies.Every cell in a person with Down syndrome will contain 47 chromosomes (with the exception of Mosaic Down syndrome which is mentioned below) instead of a normal person who has 46 chromosomes.

The arrow points to a boy with down sydrome and the extra chromosome

** What does down syndrome affect or symptoms? **

Most kids that have down syndrome have heart problems. They also have intellectual disability which means a decreaced ability to think and learn. This has to do with the brain. People with down syndrome tend to have a flattened face and nose, a short neck, a small mouth sometimes they can have a large mouth, protruding tongue, small ears, upward slanting eyes that may have small skin folds at the inner corner of their eyes. Kids with down sydrome have low muscle tone, and babies in especially may seem "floppy."This can and often change and improve over time, most children with down syndrome typically tend to develop things slower like sitting up, crawling, and walking typically later than other kids. Baby with down syndrome :(

**What are the different types of down syndrome?**

There are three different types of down syndrome. The three different types are Standard Trisomy 21, Translocation, and Mosaicism. 90 to 95% of the kids with down syndrome have Trisomy 21. It is the most common type of down syndrome and is when the extra chromosome 21 comes from either the egg or sperm cell. Translocation, another type of down syndrome, which occurs when a piece of chromosome 21 is located on another chromosome such as chromosome 14 which is the reason for the disorder. The symptoms are the same as Standard Trisomy 21 since they have three copies of chromosome 21. The person with Translocation will have 46 chromosomes but will have the genetic material of 47 chromosomes. This occurs between 3% and 5% of people with down syndrome. Mosaicism is when a person has a mix of cells, some containing 46 chromosomes and some containing 47 chromosomes. This can occur because the person got 46 chromosomes during fertilization but some how during early cell division the chromosome 21 cell pairs did not split creating a cell with 47 chromosomes and a cell with 45 chromosomes. The cell with 45 chromosomes can not live but the cell with 47 chromosomes will continue to divide. All cells that come from this cell will contain 47 chromosomes. Another reason can be because the person got 47 chromosomes at fertilization but later during cell division the extra chromosome got lost. Mosaicism occurs in 2% to 5% of cases of Down syndrome.