12/ drosophila setting up the body axis

Question 1

what components make up the a/p axis. whats segmented

Answer 1

• head, tail, thorax, abdominal region
• thorax and abdomen are segmented

Question 2

what components make up the d/v axis

Answer 2

• ventral mesoderm, ventral ectoderm, dorsal ectoderm, amnioserosa

Question 3

a/p) what does the initial maternal gradient result in, what do these result in

Answer 3

• expression of gap genes
• these define dif regions in embryo
• then lead to periodic expression of pair rule genes, which specify para segments and foreshadow segmentation of the lava
• embryo in syncytium, which ends after this point

Question 4

a/p) what do segmentation genes do? what is needed to control this process, why?

Answer 4

• elaborate patterning within each para segment
• cell to cell signalling to coordinate patterning since this happens once embryo has cellularised

Question 5

a/p) name 4/5 genes involved in a/p patterning, how are they grouped

Answer 5

• (maternal genes - provide initial grad)
• gap genes
• pair rule genes
• segmentation genes
• homeotic selector genes
• hierarchy

Question 6

a/p) name 3 classes of maternal genes

Answer 6

• Bicoid
• nanos
• torso

Question 7

a/p) bicoid: what is it an example of, where is rna localised, what else is it an example of, how is it possible

Answer 7

• morphogen - can induce multiple cell fates dep on conc
• forms a protein grad across a/p axis of syncytial embryo, rna localised at anterior end
• transcription factor - switches on dif genes at dif threshold conc
• possible bc egg is syncytium

Question 8

a/p) nanos: grad direction, function

Answer 8

• lots at posterior, less towards anterior
• represses transmission of hunchback translocation in posterior of the egg

Question 9

a/p) torso: whats it for, where are receptors present, what is trunk protein, where is it found, what is torso-like, where is it found

Answer 9

• termini of embryo, terminal signal
• everywhere
• trunk protein can form the ligand trunk
• its also everywhere
• torso like is a protease required to release trunk
• its only found at the poles
• trunk = ligand, torso = receptor

Question 10

d/v) receptor and ligand and enzymeS combo involved in d/v polarity, where are they located

Answer 10

• receptor toll everywhere
• ligand spatzel everywhere
• localised enzyme pipe creates active ligand on ventral side
• confusingly named dorsal protein acts on ventral side and suppresses dorsal features

Question 11

a/p) how does the egg get its a/p axis

Answer 11

• egg always at posterior of egg chamber
• polarity of ovariole transmitted to egg itself

Question 12

d/v) how does the egg get its d/v axis

Answer 12

• asymmetric position of nucleus
• dorsal side forms from signals released from nucleus, hence dorsal side forms closest to nucleus

Question 13

what signal is required to set up both a/p and d/v axes

Answer 13

gurken

Question 14

basic pathway of cell to cell signalling pathways

Answer 14

transmembrane receptor, ligand that binds it, tf that executes signal