Question

In Drosophila, the hunchback gene encodes a protein (HB) that is required in the correct concentrations for proper segmentation of the embryo. In the zygote and embryo, the expression of hunchback is stimulated by high concentrations of Bicoid protein. You manipulate a Drosophila embryo to have high Bicoid concentrations throughout. Which of the following would occur?

A. the HB protein would not be produced at all
B. the HB protein would be produced throughout the entire embryo
C. segmentation would not occur correctly
D. the HB protein would not be produced at all and segmentation would not occur correctly
E. the HB protein would be produced throughout the entire embryo and segmentation would not occur correctly

Answer 1

High Bicoid concentrations throughout a Drosophila embryo would result in HB protein being produced across the entire embryo and cause incorrect segmentation due to the disruption of the normal gradient that defines segment boundaries. Consequently, both the HB protein distribution and segmentation would be affected (Answer E).

Step-by-step explanation:

If you manipulate a Drosophila embryo to have high Bicoid concentrations throughout, the HB protein would be produced throughout the entire embryo and segmentation would not occur correctly. The answer to this question would be E. Bicoid protein is a morphogen that regulates the expression of the hunchback gene in a gradient manner. In a normal Drosophila embryo, the Bicoid concentration is higher at the anterior end and decreases towards the posterior end, which helps to establish the anterior-posterior axis and eventually contributes to proper segmentation.

When Bicoid concentration is unnaturally high throughout the embryo due to manipulation, it disrupts the normal gradient, leading to a uniform expression of the hunchback gene across the embryo. As a result, the necessary gradient for properly defining each segment boundary is lost, leading to incorrect segmentation.