Which one of the following statements about stem cells is correct?
During asymmetric stem cell division, only one of the daughter cells is retained as a stem cell.
Understanding Stem Cells
Stem cells are unique cells that have the ability to divide through mitosis to produce more stem cells (self-renewal) and can also differentiate into a diverse range of specialized cell types. This dual capacity is crucial for development, tissue repair, and regeneration.
Let's examine each statement about stem cells provided in the options to determine which one is correct.
Analyzing Stem Cell Statements
Statement 1: Stem Cells in Culture
The first statement says that stem cells cannot be maintained in culture because they need a specific microenvironment called niches in the body (in vivo). This is not entirely accurate. While niches are critical for regulating stem cell behavior in the body, scientists have developed methods to culture various types of stem cells in laboratories under specific conditions that mimic the niche environment or provide necessary growth factors. Therefore, stem cells can be maintained in culture.
Statement 2: Asymmetric Stem Cell Division
The second statement discusses asymmetric stem cell division. Stem cells divide in two main ways: symmetric and asymmetric. In symmetric division, a stem cell divides to produce two identical daughter cells, both of which can be either stem cells (for self-renewal) or differentiated cells (for expansion). In asymmetric division, a stem cell divides to produce two different daughter cells: one is a stem cell that maintains the stem cell pool (self-renewal), and the other is a more committed cell (often a progenitor or transit-amplifying cell) that will differentiate further. The statement accurately describes asymmetric stem cell division where only one daughter cell remains a stem cell.
Statement 3: Stem Cell Derived Transit‐Amplifying Cells
The third statement describes stem cell derived transit-amplifying cells as differentiated cells that retain the capacity to divide further. Transit-amplifying cells (also known as progenitor cells) are indeed derived from stem cells and have a limited capacity to divide rapidly. However, they are typically considered to be more committed than stem cells and are on the path to differentiation, but they are not usually described as fully 'differentiated cells'. Differentiated cells are typically post-mitotic (they no longer divide) and specialized for a specific function. Transit-amplifying cells divide to amplify the number of cells before they undergo terminal differentiation. So, while they retain division capacity, calling them 'differentiated' is imprecise; they are progenitors or precursors.
Statement 4: Hematopoietic Stem Cells (HSCs)
The fourth statement claims that Hematopoietic Stem Cells (HSCs) are totipotent stem cells. This is incorrect. Totipotent stem cells (like the zygote) have the potential to differentiate into all cell types, including the placenta. Hematopoietic stem cells (HSCs) are multipotent stem cells. Multipotent stem cells can differentiate into a limited range of cell types within a specific lineage, such as all types of blood cells (red blood cells, white blood cells, platelets) derived from HSCs, but they cannot form a whole organism or cells of unrelated lineages.
Conclusion
Based on the analysis of each statement:
- Statement 1 is incorrect because stem cells can be cultured.
- Statement 2 accurately describes asymmetric stem cell division.
- Statement 3 is imprecise in calling transit-amplifying cells 'differentiated'.
- Statement 4 is incorrect because HSCs are multipotent, not totipotent.
Therefore, the only correct statement among the options is the one describing asymmetric stem cell division.
Important Questions from Basic concepts of development
Following statements are made regarding animal development:
A. The cell is first specified towards a given fate, suggesting that it would develop into this cell type, even in a neutral environment.
B. Holoblastic rotational cleavage is observed in tunicates.
C. Infolding of sheet of cells is called ingression.
D. Conditional specification can be observed in sea urchin embryos.
Which one of the following options represents the combination of all correct statements?
C. elegans embryo uses both autonomous and conditional modes of specification. The following statements are about specification of cell lineages:
A. The signals from the P1 blastomere instructs the EMS cell for its further development.
B. In the absence of the instructive signal, the EMS cell will divide into two MS cells.
C. In the absence of the POP‐1 signal, the prospective MS cell can take up the E fate.
D. The MOM‐2 protein from the blastomere neighbouring the EMS cell instructs the dividing EMS blastomere to take up MS fate.
Which one of the following options represent both correct statements?
When 8-cell embryo of tunicates is separated into 4 blastomere pairs and allowed to grow independently in culture medium, then each blastomere pair can form most of the cell types; however, cells for nervous system are not developed. The following statements are formed from the above observations:
A. Nervous system development demonstrated autonomous specification.
B. The other tissue types are formed due to conditional specification.
C. All the tissue types, except nervous tissues that developed, demonstrated autonomous specification.
D. Nervous system development demon-strated conditional specification.
The correct combination of statements that explains the above result is:
The cells of inner cell mass of a blastocyst stage mammalian embryo are
Following statements are being made regarding specification/determination during animal development:
A. During the course of commitment, the cell may not appear different from its nearest or most distant neighbours in the embryo and show no visible signs of differentiation; but its developmental fate is restricted.
B. At the stage of specification, cell commitment is not labile.
C. A cell or tissue is determined when it is capable of differentiating autonomously even when placed into another region of the embryo, or a cluster of differently specified cells in a petri- dish.
D. Cytoskeletal arrangements maintain positioning of nuclei in the syncytium, which enables specification of these nuclei by opposing morphogen gradients namely Bicoid and Caudal in Drosophila.
E. Capacity for “mosaic" development allows cells to acquire different functions as a result of interactions with neighbouring cells.
Which of the above statements are correct?
