Chapter 28, Problem 14P

Summary Introduction

To explain: The reason that a Drosophila egg that is $bc{d}^{-}/bc{d}^{-}$ is developed normally, but the adult fruit fly will not be able to produce viable offspring.

Concept introduction:

Bicoid protein creates a morphogen gradient along the body of Drosophila and regulates the gene segmentation in concentration dependent manner. In the anterior region, bicoid protein present in a higher concentration, in central region it is present in intermediate level, and in posterior region it is present on very low concentration.