#symmetric division

Stem Cell -l

What happens when a stem cell divides symmetrically into two daughter cells that retain stemness?

Symmetric self-renewing division yields two daughter cells inheriting stemness program, adhesion molecules, and niche responsiveness, thereby doubling stem cell number per cycle. This strategy serves as primary mechanism for pool expansion during embryonic growth, after injury when rapid repopulation needed, or in optimized culture when self-renewal signals dominate. Regulatory control involves spindle orientation relative to basement membrane so both daughters remain within Wnt-rich, BMP-low niche retaining Lgr5 expression. Excessive unchecked symmetric expansion predisposes to neoplastic hyperplasia, requiring tight feedback via contact inhibition and Hippo pathway signaling to maintain tissue homeostasis balanced.

Ref: Morrison & Kimble, Nature 2006; Simons & Clevers, Cell 2011: Symmetric self-renewal expansion mechanism niche.

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Stem Cell -ll

Which type of stem cell division results in an increase in stem cell number?

Symmetric self-renewing division produces two daughters both retaining stem character, full self-renewal transcriptional program, and niche responsiveness, thereby increasing absolute stem cell number inside tissue. This mode dominates during development to rapidly expand progenitor pools, during wound healing to repopulate emptied niches, and in culture systems where niche constraints are experimentally relaxed. Mechanistically, mitotic spindle orientation parallel to niche basement membrane places both daughters within Wnt-rich microenvironment, preserving expression of Lgr5 and other stem markers. Conversely asymmetric division maintains constant numbers, while symmetric differentiating divisions generate two committed cells causing contraction.

Ref: Watt & Hogan, Science 2000; Morrison & Kimble, Nature 2006: Symmetric self-renewal expands stem pool.

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Stem Cell -lll

Which type of stem cell division stabilizes the stem cell population while producing differentiated progeny?

Asymmetric division intrinsically or extrinsically partitions fate determinants, producing one daughter retaining stem cell identity within the protective niche and another exiting to differentiate. Spindle orientation, evolutionarily conserved Par polarity proteins, Numb segregation, and polarized Notch signaling ensure unequal inheritance of transcription factors and organelles. This elegant mechanism preserves constant stem pool size during steady-state homeostasis while continuously supplying progenitors for tissue turnover. In contrast, symmetric self-renewing divisions expand pool during development, while symmetric differentiation depletes it, illustrating dynamic regulation of tissue balance throughout life.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 6: Stem cell self-renewal, asymmetric division and determinant segregation.

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PSS- Sec-F-Transport

Symmetric division in stomatal development occurs during formation of:

C fits best: Guard mother cell. Keep the PSS- Sec-F-Transport basics straight and Guard mother cell stands out as the precise answer. Avoid: A) Meristemoid; B) SLGC; D) Protodermal cell. Light and flowering items often hinge on which photoreceptor or day-length rule is in play.

Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.

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