Which one represents correct order of gastrulation events in Xenopus?

1. invagination of small group of cells in the dorsal side to form blastopore
2. gastrulation begins in the marginal zone and bottle cells line the future archenteron 
3. yolk plug forms from endodermal cells at the vegetal pole.
4. the chordamesodermal cells migrate through the blastopore lip to form the notochord
5. ectoderm spreads by epiboly to cover the entire embryo