Answer:
hope this helps
Explanation:
About 95 percent of the time, Down syndrome is caused by trisomy 21 — the person has three copies of chromosome 21, instead of the usual two copies, in all cells. This is caused by abnormal cell division during the development of the sperm cell or the egg cell.
1. courtship rituals 2. attract a mate 3. internal fertalisation occurs inside the feamales body whereas external fertalisation occurs outside the feamales body 4. <span>Gametes may get washed away 5. the devoloping zygote is protected</span>
