Xenopus are wondeful lab specimens because of their ease of isolation, large size, and coloration. In this panel, several different early cleavage stages are shown. Shown here is a late cleavage stage Xenopus embryo. Shown here is a late gastrula stage Xenopus embryo with the dorsal and ventral lips of the blastopore and yolk plug visible. We also studied the development of the common fruit fly, Drosophila melanogaster .
Drosophila development is very different from sea urchin and frog embryogenesis.
In Drosophila development, nuclear division occurs without cellular division in the early stages. Eventually, cells form at the outside of the egg membrane which is shown here. Drosophila DNA replication is unique in that certain embryonic tissues contain chromosomes that have been replicated many hundreds of times without being segregated into daughter cells. These structures are called polytene chromosomes and can be isolated from the salivary glands of Drosophila larvae. Shown here is a polytene chromosome showing a puffed out region believed to be a sight of transcriptional activity .