You perform the following experiment: Xenopus embryos aretreated early in development (before gastrulation begins) withmorpholinos to reduce the activity of Cerberus. You take an explantfrom the dorsal blastopore lip from a normal embryo at thebeginning of gastrulation cell movements and inject it into theblastocoel of a normal host embryo. You then take a dorsalblastopore lip explant from a Cerberus 'morphant' (morpholinoinjected) embryo and transfer it into the blastocoel of a normalhost embryo. You observe the effects that the normal explantcompared to the Cerberus morphant explant has on the hostembryo.
(a) What three signaling pathways are inhibited by Cerberus?
(b) BRIEFLY describe the normal function of Cerberus inpatterning the ectoderm? Where is it expressed and what does itdo?
(c) Compare the development of the host embryos with the normalblastopore lip inserted into the blastocoel and the host embryowith the Cerberus morphant blastopore lip inserted into theblastocoel.
