Is Down’s syndrome caused by an autosomal primary non-disjunction?

Down's syndrome:

1. It's a hereditary condition.
2. The nondisjunction of the 21st chromosome is the cause.
3. Chromosome 21 is an autosome.
4. Trisomy 21 is another name for this syndrome.

Non-disjunction of chromosomes:

1. It is the phenomenon that arises when the normal segregation of chromosome pairs does not occur during anaphase.
2. It can occur either in meiosis 1 or in meiosis 2.
3. When the gamete with an n+1 chromosome fuses with a normal gamete the resultant zygote has 3 copies of the same chromosome (Trisomy).
4. Yes, an autosomal primary non-disjunction causes Down's syndrome.