All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Question #1 : Help With Other Differentiation Regulation
Which of the following cells is not correctly matched to the proper classification of cell (permanent, stable, labile)?
Neuron - labile
Hepatocytes - stable
Cardiac muscle - permanent
Bone marrow - labile
Neuron - labile
Permanent cells remain in G0 and do not divide. They regenerate from stem cells, but cannot undergo division themselves. Neurons, skeletal muscle, cardiac muscle, and red blood cells are permanent cells.
Stable (quiescent) cells enter G1 from G0 when stimulated by introduction of the protein cyclin. Hepatocytes and lymphocytes are examples of stable cells.
Labile cells never go into G0 and divide rapidly with a short G1. Bone marrow, gut epithelium, skin, and hair follicles are examples of labile cells.
Example Question #2 : Help With Other Differentiation Regulation
Activation of the notch receptor by its ligand, delta, in neighboring cell populations defines patterns of distinct differentiated cell types among cells that have the potential to adopt the same fate. What is this process known as?
None of these
The correct answer is lateral inhibition. Also known as lateral specification, is a process that defines distinct cell types. This process is particularly important in vertebrate embryo nervous system development. Notch signaling is important for many developmental processes. Typically, lateral inhibition involves signaling through the notch receptor, which is stimulated by neighbor cells expressing the notch ligand, delta. Given that only neighboring cells can activate this signaling pathway, defined neighborhoods of undergo differentiation to become a distinct cell type. Morphollaxis is a term that describes regeneration of limbs without cell proliferation. Delamination describes mitotically dividing cells that split one cellular layer into two parallel layers. Furthermore, in terms of development, invagination is the initial step of gastrulation that reorganizes the embryo into a multi-layered organism with a body cavity.
Example Question #3 : Help With Other Differentiation Regulation
Which term best describes when a cell has two stable equilibrium states, but can only exist in one state at a time? States are often phenotypes.
The correct answer is bistability. Bistability is a phenomenon that is observed in signaling pathways and cell commitment to one cell fate over another cell fate by differentiation, however, either cell fate is equally likely. Lateral inhibition occurs when cells signal to neighboring cells to effect a physiological change. Quiescence is a resting, non-dividing cell state. Hysteresis is the retention of a cell-state due to feedback signaling even in the absence of the initial stimulus.