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The BCD protein is encoded by the bicoid (bcd) gene, a maternal effect gene. In Drosophila melanogaster, the bcd mRNA is normally deposited in the anterior of an egg cell by nurse cells and then becomes localized in a gradient within the cell through attachment of these bcd mRNA molecules to microtubules. When expressed early on in embryonic development, the BCD protein acts as a transcription factor, influencing gene expression and beginning differential gene expression in different parts of the developing embryo.

One easily observable manifestation of this is the formation of the cephalic furrow, an invagination in the embryo that normally develops asymmetrically towards the anterior end of the developing embryo. The cephalic furrow develops at a location in the embryo where the BCD protein reaches a threshold concentration, as shown in the image below where the blue gradient represents the BCD protein gradient.

Auman, Ann. Created for Copyright 2017. All rights reserved.

What effect on the formation of the cephalic furrow do you predict would result from a decreased amount of bcd mRNA deposited at an egg cell's anterior?


The cephalic furrow would not form.


The cephalic furrow would form at a position more anterior than normal.


The cephalic furrow would form at a position more posterior than normal.


The cephalic furrow's location would be unaffected.


The cephalic furrow would not divide the anterior from the posterior of the embryo, but rather it would divide the dorsal region from the ventral region instead.

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