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4.1 Drosophila A–P Axis — Test 1
Q1. In Drosophila, the anterior–posterior body axis is set up mainly by:✓ Maternal-effect gene products deposited in the egg
Q2. Bicoid mRNA is localised at which pole of the Drosophila egg?✓ Anterior pole
Q3. Bicoid acts as a morphogen for the Drosophila embryo because it:✓ Forms a concentration gradient specifying different fates at different levels
Q4. If bicoid mRNA is injected into the middle of a bicoid-deficient embryo, the result is:✓ A head in the middle and telson at both ends
Q5. Which maternal-effect gene products specify the ANTERIOR structures of the Drosophila embryo?✓ Bicoid and Hunchback
Q6. Nanos protein, at the posterior of the Drosophila embryo, acts to:✓ Inhibit the translation of hunchback mRNA there
Q7. Bicoid protein activates the zygotic expression of which gap gene?✓ hunchback
Q8. The opposing Bicoid (anterior) and Nanos (posterior) gradients together establish the:✓ Anterior–posterior body pattern
Q9. The earliest zygotic segmentation genes to act, dividing the embryo into broad regions, are the:✓ Gap genes
Q10. The correct order in which the three classes of segmentation genes act is:✓ Gap genes → pair-rule genes → segment-polarity genes
Q11. Pair-rule genes such as fushi tarazu (ftz) are expressed in:✓ A striped pattern in alternate segments (seven stripes)
4.1 Drosophila A–P Axis — Test 2
Q12. Fushi tarazu (ftz) belongs to which class of Drosophila segmentation genes?✓ Pair-rule genes
Q13. Giant is an example of which class of segmentation gene?✓ Gap gene
Q14. Cytoplasmic determinants in the Drosophila egg drive development by being:✓ Localised to particular regions and unequally distributed
Q15. If anterior cytoplasmic determinants are injected elsewhere in a recipient embryo, the result is:✓ Formation of an additional ectopic head
Q16. A Bicoid (anterior-class) mutation in Drosophila causes deletion of the:✓ Head and thorax (anterior structures)
Q17. A Torso (terminal-class) mutation in Drosophila causes loss of the:✓ Termini (the unsegmented ends of the embryo)
Q18. An Oskar mutation in Drosophila results in:✓ No abdomen and no pole cells (germ cells)
Q19. In Drosophila, embryos X (wild type), Y (bicoid mutant) and Z (nanos mutant) are each injected with bicoid mRNA at the posterior pole. The result is that:✓ All three develop a head at both the anterior and posterior ends
Q20. Injecting bicoid mRNA at the posterior pole of a wild-type embryo causes:✓ Head structures to form at both poles
Q21. In the syncytial Drosophila embryo, the early A-P gradients pattern nuclei because:✓ The nuclei share one cytoplasm with no separating membranes
Q22. The germ-line (pole) cells of Drosophila are specified at the:✓ Posterior pole, by the germ (pole) plasm