Correct option is A
Detailed Explanation:
Statement A: The phenotype obtained due to manipulation X can be rescued by injection of noggin in 1-cell embryo.
- This is correct. Manipulation X (exposure to UV radiation) results in a failure of cortical rotation, leading to ventralization of the embryo. The noggin protein, which inhibits BMP signaling, is a dorsalizing factor, and its injection can rescue the dorsal phenotype in embryos that otherwise would develop abnormal ventral features.
Statement B: Chordin mRNA will be enriched in embryos of manipulation X as compared to those of manipulation Y.
- This is incorrect. While chordin is a key dorsalizing factor involved in dorsal-ventral patterning, its expression is generally increased in embryos with Wnt inhibition or failure of cortical rotation (as in manipulation X). However, manipulation Y (treatment with lithium chloride to enhance Wnt signaling) typically decreases chordin expression since Wnt signaling inhibits dorsalizing factors like chordin. Thus, chordin mRNA would likely be lower in manipulation Y embryos.
Statement C: Injection of cDNA for chordin into ventral blastomeres leads to the induction of a secondary axis.
- This is correct. Chordin is a dorsalizing factor. Injection of chordin cDNA into ventral blastomeres inhibits BMP signaling, leading to the formation of a secondary axis in the developing embryo, which is a well-documented result of dorsalizing signals.
Statement D: Experimentally depleting β-catenin transcripts in 1-cell embryo by antisense oligonucleotides leads to phenotype similar to that obtained from manipulation X.
- This is correct. β-catenin is essential for Wnt signaling. Inhibition or depletion of β-catenin in 1-cell embryos leads to failure of cortical rotation, resulting in a ventralized phenotype similar to the one obtained from manipulation X, where cortical rotation is disrupted.
