down syndrome

Topics: Down syndrome, Chromosomal translocation, Chromosome Pages: 2 (766 words) Published: May 10, 2015
Translocation Trisomy 21 (Causes)
In this type of chromosomal change, only part of
an extra copy of chromosome 21 is in the cells.
The extra part of the chromosome gets "stuck"
to another chromosome and gets transmitted
into other cells as the cells divide. This type of
change causes about 4% of Down syndrome
cases. There are no distinct cognitive or medical
differences between people with translocation
trisomy 21 and those with complete trisomy 21.

!

What chromosome is affected by
this disorder?

!Chromosome 21 is one of the 23 pairs of
chromosomes in humans. People normally
have two copies of this chromosome. The
trisomy of the 21st chromosome causes

Lets go more in depth
about Down Syndrome.
Types of Down Syndrome.
The scientific name for down syndrome is
trisomy 21. With that being said, there are 3
types of down syndrome (complete trisomy 21,
mosaic trisomy 21, translocation trisomy 21).

What do you
know about
Down Syndrome?

Causes of each Down
Syndrome.
Complete Trisomy
In this case, an error during the formation of the
egg or the sperm results in either one having an
extra chromosome. So after the egg and sperm
unite, the resulting cells will also have three
copies of chromosome 21. The complete extra
copy of chromosome 21 is in all of the person's
cells—or a complete trisomy. Complete trisomy
21 is the cause of about 95% of Down syndrome
cases.

Mosaic Trisomy 21
Not every cell in the body is exactly the same. In
about 1% of Down syndrome cases, most of the
cells in the body have the extra chromosome, but
some of them don't. This is called "mosaicism."
Mosaic trisomy 21 can occur when the error in
cell division takes place early in development but
after a normal egg and sperm unite.

Down Syndrome Symptoms

By: Jennifer Weller
Biology Period 7

Not So Fun Facts After All…

How do you get Down Syndrome?
In most cases of down syndrome, its usually not
inherited. When the condition...
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