Correct option is C
Explanation-
Statement A - Microinjection of bicoid mRNA in the middle of a bicoid-deficient embryo leads to formation of ‘head’ in the middle and telson at the two ends - Correct
Bicoid is a maternal effect gene and acts as a morphogen. It is normally localized at the anterior end, where it specifies head and thorax structures. In a bicoid-deficient embryo, if you inject bicoid mRNA in the center, it creates a new anterior (head) structure in the center, and the posterior ends (telson) form on both sides. This experiment proved that bicoid functions in a concentration-dependent manner to specify positional identity.
Statement B - Nanos protein inhibits the translation of caudal mRNA at the posterior half of the embryo - Incorrect
Nanos is a posterior determinant in Drosophila. However, Nanos inhibits the translation of hunchback mRNA, not caudal. In fact, Bicoid inhibits caudal mRNA translation at the anterior, not Nanos at the posterior.
Statement C - The Bicoid protein activates the zygotic expression of the hunchback gene - Correct
Bicoid acts as a transcription factor for zygotic hunchback gene expression in the anterior part of the embryo. This is essential for proper head and thorax development.
Statement D - The segment polarity genes are expressed in segments of the embryo - Correct
Segment polarity genes (e.g., engrailed, wingless) are expressed within each segment and help define the anterior-posterior axis within segments. Their expression maintains segment boundaries and polarity.
Final Answer: A, C, and D only (Correct option: c)
B is incorrect because it mixes up the targets of Bicoid and Nanos.
