What are the causes of Down's syndrome?

Question

I always thought it was because you had a child late in life

Answer 1

Down syndrome, Down's syndrome, or trisomy 21 is a chromosomal disorder caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British doctor who described the syndrome in 1866.

It has nothing to do with your age.

Answer 2

Downs is caused by an extra chromosome in the cell.  

Answer 3

The truth is:

1. Down'sSyndrome is caused by having one extra chromosome number 21.

2. It can occur in two ways:

a.) by non-disjunction which occurs more often in OLDER eggs (the last nuclear division occurs AFTER fertilization of the egg) and this occurs much more commonly in older mothers.

b.) by a "Robertsonian Translocation" in which a part of the chromosome 21 is broken-off and is attached to the chromosome 14 (which sorts independently from the chromosome 21)

3. In the latter situation, four possibilities occur:

a.) the resulting zygote gets both of the normal 14 and 21

b.) the zygote gets the broken 21 and 14 with the extra piece and the resulting person would be a "carrier"

c.) the zygote get the broken 21 and the normal 14 (these pregnancy do not survive.)

d. the zygote get the normal 21 and the 14 with the extra piece of 21 and the resulting person has Down's.

This Robertsonian's version IS NOT associated with age.

Old OB Doc

Sorry for the long-winded answer

Answer 4

it is because they have extra chromosones

People who have babies later than 40 are more at risk to having babies that are down syndrom, along with many other conditions but many woman have perfectly healthy babies.  

Answer 5

non-disjunction of I think chromosome 21.  This means that during meiosis the chromosomes don't separate properly.  In other words the zygote will have one too many chromosomes.  Its more frequent late in life as some cellular degeneration of gametes takes place in the woman.