Assertion [a]: A zygote and its immediate descendant cells are unspecialized and are called totipotent
Reason [r]: Totipotent cells retain the capacity to differentiate into only a few cell types
Assertion and Reason Analysis: Totipotency
Analysis of Assertion [a]
Assertion [a] states: A zygote and its immediate descendant cells are unspecialized and are called totipotent.
- Truthfulness: This statement is true.
- Explanation: The zygote, formed by fertilization, and the initial few cells produced through its cleavage divisions (like blastomeres) are indeed unspecialized. They possess the potential to develop into a complete organism, including embryonic and extraembryonic tissues. This characteristic defines them as totipotent.
Analysis of Reason [r]
Reason [r] states: Totipotent cells retain the capacity to differentiate into only a few cell types.
- Truthfulness: This statement is false.
- Explanation: Totipotent cells have the broadest differentiation potential. They can differentiate into *all* possible cell types required to form a complete organism, not just a few. Cells limited to differentiating into a few specific cell types are typically multipotent or pluripotent, not totipotent.
Conclusion
Based on the analysis:
- Assertion [a] is true.
- Reason [r] is false.
Therefore, the correct option is the one stating that [a] is true and [r] is false.
Important Questions from Totipotency and Plant Regeneration
- Determine the correctness or otherwise of the following Assertion [a] and the Reason [r]
Assertion [a]: It is possible to regenerate a whole plant from a single plant cell.
Reason [r]: It is easier to introduce transgenes in to plants than animals. - A dioecious plant has XX sexual genotype for female and XY for male. After double fertilization, what would be the genotype of the embryos and endosperms?
- Shoot organogenesis by tissue culture results into
Determine the correctness or otherwise of the following Assertion and Reason (r).
Assertion: In direct somatic embryogenesis, embryos are developed without going through callus formation.
Reason: This is possible due to the presence of pre-embryonically determined cells.
