MCB 141 Quiz 2
11 February 2013
Name:
Section 1: Identify the term using the fewest words possible. 1pt each
1. Insulator - Segment of DNA which prevents an enhancer from crossing over to a
neighboring gene.
2. Hunchback -Gap gene repressor expressed in the anterior part of the fly embryo
3. Short Range Repressor -Repressor which inactivates enhancers within a
~200bp distance brom where it binds
4. Antennapedia mutant - Mutation which results in the expression of
Antennapedia in the head, transforms antennae into legs
5. Bithorax Complex - Collinear complex of Hox genes controlling posterior
segment identity. Contains Ubx, AbdA and AbdB
6. Homeotic Mutant - Mutant where one segment takes on the identity of another
segment ie T3 having wings instead of halteres in the Ubx mutant.
Section 2: Answer the following questions. (2pts each)
1. What are two ways you could modify the Giant enhancer that might expand
expression towards the posterior (so that it more closely matched
Hunchback)?
1) Make bicoid binding sites stronger 2) Add additional bicoid binding sites
2. The Eve stripe 2 enhancer is repressed by Giant and Kruppel. There are 2
gaps where neither Giant nor Kruppel is expressed, one in the anterior of the
embryo and one in the posterior. Why does the Eve stripe 2 enhancer only
drive expression in the anterior gap?
Eve stripe 2 is activated by Bicoid which is only present in the anterior of the
embryo. In the posterior domain where Giant and Krupel are not expressed the Eve
2 enhancer is inactive because there is no Bicoid to turn it on.
3. If Abd-B expression is eliminated what gene will control the identity of the
segments where it is normally expressed (A5-A8)? Which segment will they
look like?
AbdA would control identity and the segments would look like A1-A4 (anterior
abdomen)