Monday, October 4, 2010

day four...

there is perfection in imperfection....
random fact about down syndrome #4: there are three types of down syndrome (or three ways that it can occur)... the first covers 95% and is known as trisomy 21...prior to or at conception a pair of the 21st chromosome fails to seperate creating three copies instead of just two...as the fetus develops the extra chromosome is replicated in every cell of the body. the second covers 4% of cases....it is known as translocation....this occurs when a part of the 21st chromosome breaks off and attaches itself to another...usually chromosome 14...the child will still have the usual 46 chromosomes in this case, but the presence of that extra portion of the 21st chromosome causes the characteristics of down syndrome. the last is known as mosaicism and accounts for 1% of cases...this happens when the 21st chromosome splits after fertilization...but not in every cell...so some cells will have the usual 46 and some will have the characteristic 47.

1 comment:

Our ScrapBook...