AP axis and segmentation in drosophila Flashcards
How do transcription factors direct transcription?
By binding to CIS regulatory, enhancer or suppressor regions of DNA.
The effects of transcription factors are additive. True or false?
True.
Transcription factors are all the same strength. True or false?
False.
Cell respond to varying concentrations of transcription factor. What do a) low affinity and b) high affinity regions of DNA respond to?
a) High concentrations
b) Low concentrations
Which genes regulate gap gene expression?
Egg polarity genes.
Are egg polarity genes zygotic or maternal?
Maternal.
Gap genes can regulate each other. What is the purpose of this?
To tighten boundaries and create distinct developmental domains.
Give an example of two gap genes regulating each other.
Kruppel and Hunchback are mutually repressive.
Which genes regulate pair rule genes? Give an example.
Gap genes.
Ftz is a pair rule gene: each stripe of ftz expression is activated by different combinations of gap genes.
How can Transgenesis be activated?
Via heat-shock.
Which regions are more important in the regulation of transcription, enhancer or suppressor regions?
Suppressor.
Which gap genes suppress eve2, a pair rule gene?
Giant and Kruppel supress eve2.
Which gap and egg polarity genes enhance eve2, a pair rule gene?
Hunchback and bicoid.
What are the first 3 segment polarity genes to be activated?
- Engrailed (en).
- Wingless (wg)
- Hedgehog (hh)
Which genes activate segment polarity genes?
Pair rule genes.
Wingless is a pair rule gene. What is it?
A signalling protein.
Wingless signalling activates hedgehog in every segment. How?
- Wingless (wg) binds to frizzled (fz) in the membrane
- Frizzled (fz) activates dishevelled (dsh) in the cytoplasm
- Dishevelled activates zeste-white3 (zw3)
- zw3 activates armadillo (arm)
- Armadillo is released into the nucleus and activates the transcription of engrailed (en) and hedgehog (hh)
Hedgehog behaves like a morphogen. True or false?
True.
What kind of relationship do wingless (wg) and hedgehog (hh) have?
Mutually dependent.
Hedgehog signalling activates wingless. How?
- Hedgehog, in the presence of Dally and Dlp, binds to patched (ptc) in the membrane
- Patched no longer inhibits smoothened (smo)
- Smo activates cubitus interuptus (Ci) in the cytoplasm
- Ci enters the nucleus to activate wingless
Wingless behaves like a morphogen. True or false?
True.
Both wingless and hedgehog signalling acts within segments. True or false?
True.
If you remove any elements in either the wg or hh pathways, what will happen?
Both wg and hh will cease to be activated as they are necessary for each other’s expression.
What is the diffusion of wg and hh within segments like?
Asymmetric as they are acting as morphogens.
Wg and hh restrict each other’s diffusion. True or false?
True.
What are the homologues of wingless in vertebrates?
Wnt genes.
What do vertebrate wnt genes do?
Regulate cell patterning and proliferation.
What disease are wnt genes heavily implicated in?
Cancer.
What are the homologues of hedgehog in vertebrates?
Sonic hedgehog (shh), desert hedgehog (dhh) and indian hedgehog (ihh).
Thus what are the pair rule genes in a) invertebrates and b) vertebrates?
a) wingless (wg) and hedgehog (hh)
b) wnt and sonic/desert/indian hedgehog (s/d/ihh)
