lec 11- specification of segment identities

Question 1

what is it called when the structures that are not visible on the embryo, develop later during embryogenesis?

Answer 1

imaginal discs

Question 2

what do homeotic selector genes do?

Answer 2

give the segments identities (e.g. give segment one the ability to form legs during morphogenesis)

Question 3

what is homeosis?

Answer 3

the transformation of a segment or structure into a different segment or structure

Question 4

does the homeotic genes in Drosophila encode transcription factors that have a DNA sequence called the homeobox DNA motif?

Answer 4

yes

Question 5

what is the name of the protein domain the homeobox DNA motif encodes for?

Answer 5

homeodomain, which controls binding of the protein to DNA

Question 6

what are Hox genes?

Answer 6

genes that contain the homeobox DNA motif and result in the transformation of one segment into another when they are mutated

Question 7

what are the two gene clusters that the homeotic genes are arranged in, in the Drosophila genome?

Answer 7

antennapedia complex and the bithorax complex

Question 8

which side of the gene is expressed earlier, 3’ or 5’?

Answer 8

3’

Question 9

what are known as the master regulatory genes of embryogenesis?

Answer 9

homeotic genes

Question 10

what are the 3 genes that are expressed in the bithorax complex?

Answer 10

Ubx (parasegments 5-12), abd-A (parasegments 7-13), Abd-B (parasegments 10 and onwards)

Question 11

how were the identities of the segments bithorax complex helps develop tested?

Answer 11

by removing the bithorax complex, it was found out that the development from 3-4 occurred the same, but when it came to segments 5-13, they stayed the same as parasegment 4 which indicates that the bithorax complex is important in the correct development of segments 5-13

Question 12

if only Ultrabithorax was added while the rest of the bithorax complex was gone, what occurred?

Answer 12

-one parasegment 4 was developed, one 5 and eight parasegment 6’s were developed
-this indicates that ultrabithorax has effects in specifying segments 5 and more, but it is only able to fully develop the identities of parasegment 5 and 6, rather than all

Question 13

if Ultrabithorax was added with abd-A while the rest of the bithorax complex was gone, what occurred?

Answer 13

-the parasegments 5,6,7,8, and five 9 developed
-indicating that abd-A must affect parasegment 7 and more, and if both are present it can specify 7,8, and 9
-this means Abd-B must specify 10 onwards