Correct option is B
In Drosophila, the segmentation process is regulated by a hierarchy of genes that act in a specific order. The correct sequence of gene activity during early segmentation is:
Maternal genes: These are the first genes to be activated and set up the initial patterning of the embryo along the anterior-posterior axis. They encode proteins and RNAs deposited by the mother that establish gradients in the egg.
Gap genes: These genes are activated by maternal gene products and help subdivide the embryo into broad regions. They regulate the expression of pair-rule genes.
Pair-rule genes: These genes are responsible for creating a segmented pattern in the embryo by defining the boundaries of each segment.
Segment polarity genes: These genes refine the patterning further and establish the anterior-posterior polarity within each segment.
Information Booster:
Maternal genes control the overall patterning of the early embryo by providing positional information.
Gap genes break down the embryo into large segments by responding to maternal gradients.
Pair-rule genes define the boundaries of alternating segments, and they are expressed in a repeated, periodic pattern.
Segment polarity genes refine the segmental pattern and are involved in defining the polarity within individual segments.
The maternal-to-gap-to-pair-rule-to-segment polarity hierarchy ensures that the segmented body plan is established correctly during early development in Drosophila.
This gene hierarchy is essential for establishing the correct spatial pattern of the developing embryo, ensuring proper segmentation and body structure.
