Developmental genetics

Question 1

There are three main mechanisms of differential gene expression in developmental genetics, which are these?

Answer 1

1. Cellular localization of RNA, often at different poles.
2. Cell-cell signaling. Inhibition signals so that only the closest cells of the signaling substance differentiate.
3. Paracrine signaling via hormones. Depends on the hormone concentration, the cell receptor density, the number of transcriptional binding sites, nature of the ligand-receptor interaction.

Question 2

How is the ventral / dorsal axis determined embryonically?

Answer 2

Dorsal side of the embryo has less toll-like receptors (TLRs). The TLRs will be bound by the “Späzle lignad” which releases the protein dorsal from its complex with cactus.

Dorsal’s downstream interacttions include:
1. Rhomboid
2. Twist
3. SOG

Question 3

How is the anterior / posterior axis determined embryonically?

Answer 3

The localization of bicoid and oscar mRNA.
- The 3’UTRs of oscar and bicoid are important. If you
exchange one for the other, no axis is defined.

bicoid reduces expression of hunchback which in turn regulate several morphogenes.
1. Giant (anterior)
2. Giant (posterior)
3. Kruppel
4. knirps

Question 4

What are morphogenes?

Answer 4

Morphogenes together with hox-genes govern developmental patterns. There are multiple “pair-rule genes” which alternate in the embryo, this is one of the patterns.