Asymmetric cell division Flashcards
lecture 21
What is asymmetric cell division?
A process where a parent cell divides into two daughter cells with distinct fates or characteristics.
Why is asymmetric cell division important in multicellular organisms?
It is critical for development and differentiation into various tissue types from a single cell.
What distinguishes symmetric from asymmetric cell division?
Symmetric division produces identical daughter cells, whereas asymmetric division creates daughter cells with different fates or properties.
What components are distributed asymmetrically during cell division?
Proteins, RNAs, lipids, histone modifications, DNA methylation, organelles (e.g., old mitochondria), cytoskeletal elements, cell fate components, reactive species, and protein aggregates.
How does asymmetric cell division maintain tissue homeostasis?
By balancing stem cell self-renewal and differentiation, supporting tissue repair and preventing aging or cancer.
What happens if tissue homeostasis balance is disrupted?
cancer or tissue aging and degeneration.
How does asymmetric cell division benefit germ cells?
It rejuvenates germ cells, ensuring they are free from biological damage and capable of passing the genome to the next generation.
What is inherited by the “less fit” cell during germ cell division?
Senescence factors
Who first observed a segregating determinant in asymmetric cell division?
Ed Conklin in 1905, studying the ascidian egg.
What discovery was made using Drosophila sensory organs?
The asymmetric segregation of the protein Numb, revealing mechanisms of asymmetric division.
What are the three steps of asymmetric cell division?
1.Establishment of a polarity axis.
2.Orientation of the mitotic spindle along this axis.
3.Coordination of spindle orientation with cell fate determinant positioning.
What role do PAR proteins play in asymmetric cell division?
They establish cortical polarity and are asymmetrically localized to guide cell division.
Why is C. elegans a model organism for studying asymmetric cell division?
Its zygote shows intrinsic polarization, with processes like acto-myosin flow and centrosome signals driving polarity.
What tools are used to study asymmetric cell division in C. elegans?
Temperature-sensitive mutations, inducible targeting (e.g., nanobodies), and optogenetics.
How is spindle orientation achieved in asymmetric cell division?
Through the evolutionary conserved machinery involving PAR proteins and centrosome activity.
What is the fate of the mother centrosome during division?
It is inherited by the cell undergoing differentiation and sheds pericentriolar material (PCM) to decrease activity.
How are cell fate determinants asymmetrically segregated?
Polarity regulators and kinase reactions guide the localization of proteins and RNAs into specific daughter cells.
What are examples of cell fate determinants in Drosophila neuroblasts?
Numb (inhibits Notch signaling), Miranda, Staufen, Prospero, and Brat.
What determines the position of the cytokinetic furrow in division?
Cortical polarity and astral microtubules regulate contractility and guide cytokinesis placement.
How is the mitotic spindle positioned?
Through dynein and kinesin motor balance and centrosome dynamics.
How is polarity establishment timed with cell cycle progression?
Surveillance mechanisms ensure division occurs only after polarity is established.
What kinase is critical in coordinating polarity and spindle orientation?
Aurora A kinase.
What is the central challenge in asymmetric cell division?
Coordinating spindle orientation with the asymmetric segregation of cellular components to maintain self-renewal and differentiation.
