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
Causes of each Down
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 is caused by trisomy
21, the chromosomal abnormality occurs as a