Q26 - Homeotic Genes Define Flower and Body Segment Identity
Arabidopsis flowers are formed incorrectly when the pistillata, apatela2 or agamous genes are knocked-out, as shown. Genes which determine the identity of parts of an organism are called homeotic selectors (or HOX genes in animals). HOX genes expressed more posteriorly (towards the anus) tend to repress those expressed more anteriorly (towards the head).
Using the information and data, determine which of the statements are true or which are false.
A. Homeotic selector genes tend to have small and simple promoters compared to other genes.
B. PISTILLATA expression is necessary for cells to determine they should become part of a flower.
C. Expression of AGAMOUS causes floral meristems to stop growing after four whorls.
D. The antennapedia mutation is a loss of function, or knock-out, mutation.
E. All these genes are first expressed once a cell is specialising/differentiating into its final role.
Question reproduced from IBO 2017, Theoretical Exam B, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Official answer key & worked solutions