AP axis and segmentation in drosophila

Question 1

How do transcription factors direct transcription?

Answer 1

By binding to CIS regulatory, enhancer or suppressor regions of DNA.

Question 2

The effects of transcription factors are additive. True or false?

Answer 2

True.

Question 3

Transcription factors are all the same strength. True or false?

Answer 3

False.

Question 4

Cell respond to varying concentrations of transcription factor. What do a) low affinity and b) high affinity regions of DNA respond to?

Answer 4

a) High concentrations

b) Low concentrations

Question 5

Which genes regulate gap gene expression?

Answer 5

Egg polarity genes.

Question 6

Are egg polarity genes zygotic or maternal?

Answer 6

Maternal.

Question 7

Gap genes can regulate each other. What is the purpose of this?

Answer 7

To tighten boundaries and create distinct developmental domains.

Question 8

Give an example of two gap genes regulating each other.

Answer 8

Kruppel and Hunchback are mutually repressive.

Question 9

Which genes regulate pair rule genes? Give an example.

Answer 9

Gap genes.

Ftz is a pair rule gene: each stripe of ftz expression is activated by different combinations of gap genes.

Question 10

How can Transgenesis be activated?

Answer 10

Via heat-shock.

Question 11

Which regions are more important in the regulation of transcription, enhancer or suppressor regions?

Answer 11

Suppressor.

Question 12

Which gap genes suppress eve2, a pair rule gene?

Answer 12

Giant and Kruppel supress eve2.

Question 13

Which gap and egg polarity genes enhance eve2, a pair rule gene?

Answer 13

Hunchback and bicoid.

Question 14

What are the first 3 segment polarity genes to be activated?

Answer 14

1. Engrailed (en).
2. Wingless (wg)
3. Hedgehog (hh)

Question 15

Which genes activate segment polarity genes?

Answer 15

Pair rule genes.

Question 16

Wingless is a pair rule gene. What is it?

Answer 16

A signalling protein.

Question 17

Wingless signalling activates hedgehog in every segment. How?

Answer 17

1. Wingless (wg) binds to frizzled (fz) in the membrane
2. Frizzled (fz) activates dishevelled (dsh) in the cytoplasm
3. Dishevelled activates zeste-white3 (zw3)
4. zw3 activates armadillo (arm)
5. Armadillo is released into the nucleus and activates the transcription of engrailed (en) and hedgehog (hh)

Question 18

Hedgehog behaves like a morphogen. True or false?

Answer 18

True.

Question 19

What kind of relationship do wingless (wg) and hedgehog (hh) have?

Answer 19

Mutually dependent.

Question 20

Hedgehog signalling activates wingless. How?

Answer 20

1. Hedgehog, in the presence of Dally and Dlp, binds to patched (ptc) in the membrane
2. Patched no longer inhibits smoothened (smo)
3. Smo activates cubitus interuptus (Ci) in the cytoplasm
4. Ci enters the nucleus to activate wingless

Question 21

Wingless behaves like a morphogen. True or false?

Answer 21

True.

Question 22

Both wingless and hedgehog signalling acts within segments. True or false?

Answer 22

True.

Question 23

If you remove any elements in either the wg or hh pathways, what will happen?

Answer 23

Both wg and hh will cease to be activated as they are necessary for each other’s expression.

Question 24

What is the diffusion of wg and hh within segments like?

Answer 24

Asymmetric as they are acting as morphogens.

Question 25

Wg and hh restrict each other’s diffusion. True or false?

Answer 25

True.

Question 26

What are the homologues of wingless in vertebrates?

Answer 26

Wnt genes.

Question 27

What do vertebrate wnt genes do?

Answer 27

Regulate cell patterning and proliferation.

Question 28

What disease are wnt genes heavily implicated in?

Answer 28

Cancer.

Question 29

What are the homologues of hedgehog in vertebrates?

Answer 29

Sonic hedgehog (shh), desert hedgehog (dhh) and indian hedgehog (ihh).

Question 30

Thus what are the pair rule genes in a) invertebrates and b) vertebrates?

Answer 30

a) wingless (wg) and hedgehog (hh)

b) wnt and sonic/desert/indian hedgehog (s/d/ihh)