Practice Questions

TLS Online TPP Program

#Question id: 7297

How is the ABC model for floral identity in Arabidopsis similar to the models for homeotic gene function derived from studies in Drosophila?

#Unit 5. Developmental Biology

The key resposnsibility of homeotic genes in both is patterning of dorsal-ventral asymmetry.
In both organisms, one homeotic gene is expressed at the two ends, a second expressed in to domains more central to that of the first and a third expressed more centrally, thus contributing unambiguous identities to all regions of the organism.
In both organisms, homeotic genes interact, so that it is often the combination of genes present that is critical in specifying structure in adult.
The ABC model of Arabidopsis is essentially identical to the Drosophila model for homeotic gene function, in that the Drosophila version of the A gene is abdominal-A, the Drosophila version of the B gene is Abdominal-B, and the Drosophila version of the C gene is Ultrabithorax.

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#Question id: 14764

#Unit 2. Cellular Organization

Match the following proteins (Column I) with their function (Column II). Which of the following is correct?

Column I	Column II
a. Profilin	i. binds to the (+) end of an actin filament, thereby inhibiting subunit addition or loss.
b. Cofilin	ii. blocks (−) ends, inhibits filament disassembly, to stabilize filaments
c. Thymosin-β4	iii. involved in actin treadmilling, but it binds specifically to F-actin in which the subunits contain ADP
d. Cap Z	iv. binds ADP–G-actin and catalyzes the exchange of ADP for ATP
e. Tropomodulin	v. binds to ATP–G-actin in such a way that it inhibits addition of the actin subunit to either end of the filament.