ex18 Flashcards
What are the common methods a cell uses to turn off or reduce gene expression?
Methods include transcriptional repression, DNA methylation, histone modification, and RNA interference (RNAi).
What mechanisms prevent a transcription factor from inappropriately influencing adjacent genes?
Insulator sequences, chromatin compartmentalization, and chromatin remodeling proteins prevent inappropriate cross-talk between genes.
How do differentiated cells maintain their identity and establish cell memory?
Differentiated cells maintain identity through epigenetic modifications, transcriptional feedback loops, and non-coding RNAs, ensuring stable gene expression.
What are the two most common molecular switches in cells?
Phosphorylation and GTP-binding proteins (G proteins) are the two main molecular switches, regulating protein activity.
How do positive and negative feedback regulation operate in intracellular signaling pathways?
Positive feedback amplifies signals (e.g., MAPK activation), while negative feedback dampens signals (e.g., NF-κB pathway regulation).
How does calmodulin operate in the cell and regulate CaM-kinase?
Calmodulin binds calcium, undergoes a conformational change, and activates CaM-kinase, which regulates various cellular processes like metabolism and gene expression.
What actions does the anaphase promoting complex (APC/C) perform during the metaphase-to-anaphase transition?
APC/C promotes the degradation of cyclin B and securin, triggering the separation of sister chromatids by activating separase.
What is the extrinsic pathway of apoptosis?
The extrinsic pathway is activated by death ligands binding to death receptors, triggering a cascade of caspase activation leading to apoptosis.
How was the Rb gene identified and how can it cause cancer?
The Rb gene was identified through studies of retinoblastoma, and mutations cause cancer by disrupting cell cycle regulation at the G1-S checkpoint.
How do cadherins mediate cell-cell interactions and contribute to cancer progression?
Cadherins facilitate cell adhesion, but in cancer, loss of E-cadherin promotes cell detachment and metastasis.
How do mutations in the PI3-kinase/Akt/mTOR pathway drive cancer growth?
Mutations lead to continuous activation of Akt and mTOR, promoting cell survival, growth, and metabolic activity in cancer cells.
What is genomic imprinting?
An epigenetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner, with one allele being silenced while the other is expressed.
What is CRISPR?
A genome-editing tool that allows for precise modifications of DNA using a guide RNA and Cas9 enzyme to introduce double-strand breaks, enabling gene disruption or insertion.
What are MAP kinases?
Signaling molecules that regulate various cellular processes, such as growth, differentiation, and stress responses, through phosphorylation cascades activated by extracellular signals.
What are kinesins?
Motor proteins that transport cellular cargo along microtubules, playing a key role in intracellular transport and mitosis, including spindle formation and chromosome movement.
