BIOL 103 Midterm 2

MAPKKK (Raf)

Mitogen-Activated Protein Kinase Kinase Kinase; the upstream kinase activated by Ras that phosphorylates and activates MAPKK.

MAPKK (MEK)

Mitogen-Activated Protein Kinase Kinase; the intermediate kinase activated by Raf that phosphorylates and activates MAPK (ERK).

MAPK (ERK)

Mitogen-Activated Protein Kinase; the downstream kinase activated by MEK that translocates to the nucleus to phosphorylate transcription factors driving cell proliferation.

phospho-ERK (p-ERK)

The active, phosphorylated form of ERK that signals for downstream transcription and cell proliferation.

Ras

A small GTPase protein (proto-oncogene) that acts as an molecular switch; active when bound to GTP and inactive when bound to GDP.

GPCR

G-Protein Coupled Receptor; a cell-surface receptor with 7 transmembrane domains that undergoes a conformational change upon ligand binding to activate an intracellular G-protein.

G-alpha Subunit

The subunit of a G-protein that exchanges GDP for GTP upon GPCR activation and dissociates to stimulate downstream effectors like adenylyl cyclase.

Adenylyl Cyclase

An enzyme activated by G-alpha that converts ATP into cyclic AMP (cAMP), a secondary messenger in signaling cascades.

Second Messenger

Small non-protein molecules/ions (e.g., cAMP, Ca2+) that rapidly relay and amplify signals inside the cytoplasm.

GTP Hydrolysis

The enzymatic conversion of GTP to GDP that inactivates G-proteins or Ras, terminating the intracellular signal.

p53

A major tumor suppressor protein activated by DNA damage; induces transcription of p21 for cell cycle arrest or triggers apoptosis if damage is unrepairable.

p21

A CDK-inhibitor protein transcribed by p53 that binds to and inactivates G1/S-Cdk and S-Cdk complexes to halt the cell cycle.

Rb (Retinoblastoma Protein)

A tumor suppressor protein that holds and inactivates transcription factors; when phosphorylated by CDKs, it releases them to allow cell proliferation.

Bax

A pro-apoptotic protein that promotes outer mitochondrial membrane permeability and triggers programmed cell death.

Bcl-2

An anti-apoptotic, pro-survival protein that inhibits Bax and prevents programmed cell death.

CDK (Cyclin-Dependent Kinase)

A kinase involved in cell cycle regulation that is continuously expressed but requires binding of a specific cyclin protein to become active.

Cyclin

A regulatory protein whose concentration fluctuates throughout the cell cycle; binds to CDKs to drive progression past cell cycle checkpoints.

Telomeres

Repetitive non-coding DNA sequences at the ends of linear chromosomes that protect coding regions from shortening during replication cycles.

Telomerase

A reverse transcriptase enzyme carrying its own RNA template that extends parental chromosome ends to counteract the end-replication problem.

Loss-of-Function Mutation

A mutation resulting in a protein losing its normal biological activity; typically recessive.

Gain-of-Function Mutation

A mutation causing a protein to gain a new activity or become hyperactive/constitutively active; typically dominant.

Anchorage Dependence

The requirement that normal cells must be attached to a solid substratum to divide; cancer cells lose this property and can metastasize.

Density-Dependent Inhibition

The phenomenon where crowded cells stop dividing; cancer cells lose this property and continue dividing in dense clusters.

RT-PCR

Reverse Transcription Polymerase Chain Reaction; a molecular technique used to detect and quantify mRNA expression levels by converting RNA to cDNA first.

Immunohistochemistry (IHC)

A technique using antibody staining to visualize the presence and spatial distribution of specific proteins within intact tissue samples.

Reporter Assay

An experimental setup fusing a gene's promoter/regulatory region to a visible marker (e.g., GFP) to track where and when that promoter is actively transcribed.

Flow Cytometry

A laser-based technique used to analyze fluorescence per cell, often measuring cellular DNA content to evaluate cell cycle distribution (G1, S, G2/M).

Totipotent

Stem cells that have the capacity to differentiate into any cell type in the body as well as extraembryonic/placental tissues.

Pluripotent

Stem cells capable of giving rise to almost all cell types in the adult body except extraembryonic tissues.

Multipotent

Stem cells capable of differentiating into a limited range of specialized cell types within a specific tissue or lineage.

Endocrine Signaling

Long-distance cell signaling where molecules (hormones) travel through the bloodstream to reach distant target cells.

Paracrine Signaling

Local cell signaling where molecules diffuse through the extracellular fluid to act on nearby target cells.

Autocrine Signaling

Cell signaling where a cell secretes a signal molecule that binds to receptors on its own surface.

Contact-Dependent Signaling

Signaling that requires direct physical contact between membrane-bound molecules of adjacent cells.

G1 Checkpoint

The restriction point where the cell assesses environmental conditions, growth factor signals, and DNA damage before committing to DNA replication.

G2 Checkpoint

The cell cycle checkpoint that verifies whether DNA replication was completed accurately without damage before entering mitosis.

M Checkpoint

The spindle assembly checkpoint that ensures all chromosomes are properly attached to the mitotic spindle before anaphase begins.

G0 Phase

A non-dividing, quiescent state entered by cells that do not receive stimulatory signals to pass the G1 checkpoint.

Epigenome

Heritable chemical modifications to DNA or histones (e.g., methylation, acetylation) that alter gene expression without changing the primary DNA sequence.

DNA Methylation

The addition of methyl groups to cytosine bases in DNA (often CpG islands), typically associated with gene silencing and chromatin condensation.

Histone Acetylation

The addition of acetyl groups to histone tails by HATs, which loosens chromatin structure (euchromatin) and promotes active transcription.

Histone Deacetylation

The removal of acetyl groups from histones by HDACs, causing chromatin to condense (heterochromatin) and repressing gene expression.

Promoter

A regulatory DNA sequence upstream of a coding region where RNA polymerase and general transcription factors bind to initiate transcription.

Enhancer

A regulatory DNA sequence that can be located far from the gene; binds specific transcription factors (activators) to greatly increase transcription.

Transcription Factors

Proteins that bind to specific DNA regulatory sequences to promote or repress the recruitment of RNA polymerase, determining tissue-specific gene expression.

Induced Pluripotent Stem Cells (iPSCs)

Adult somatic cells reprogrammed back into a pluripotent state by introducing specific key transcription factors.

Apoptosis

Regulated, programmed cell death used during development, tissue remodeling, or to eliminate damaged or infected cells.

Cellular Differentiation

The process by which an unspecialized cell (like a stem cell) acquires specialized structures and functions by expressing a unique subset of genes.

Organogenesis

The phase of embryonic development where tissues organize and differentiate into functional organs, driven by cell movement, signaling, and proliferation.

Cell Movement (Morphogenesis)

The coordinated migration of cells during embryonic development to form structural layers and distinct shapes within tissues.

Extrinsic Apoptosis Pathway

Programmed cell death triggered by external death ligands binding to cell-surface death receptors.

Intrinsic Apoptosis Pathway

Programmed cell death triggered by internal cellular stress or DNA damage, regulated by mitochondrial membrane permeabilization (Bax/Bcl-2 balance).

Western Blot

A laboratory method that uses specific antibodies to detect, quantify, and measure the phosphorylation state of specific proteins in a cell lysate.

Loading Control

A housekeeping protein (e.g., Actin, GAPDH, Tubulin) probed on a Western blot to ensure equal amounts of total protein were loaded into each lane.

cDNA (Complementary DNA)

DNA synthesized from a single-stranded mRNA template via reverse transcriptase; lacks introns and represents actively transcribed genes.

Negative Feedback Loop

A regulatory mechanism where a downstream output (e.g., active ERK) inhibits upstream components (e.g., Raf or MEK) to attenuate signaling duration and strength.

Propidium Iodide

A fluorescent DNA-binding dye used in flow cytometry to measure cellular DNA content and determine the proportion of cells in G1, S, or G2/M phases.

Senescence

A state of permanent cell cycle arrest that normal somatic cells enter when telomeres become critically short or after unrepairable cellular stress.

Proto-oncogene

A normal cellular gene (e.g., Ras) that promotes cell growth and division; gain-of-function mutations transform it into an oncogene, causing excessive proliferation.

Tumor Suppressor Gene

A gene (e.g., p53, Rb, p21) whose normal protein product inhibits cell division or repairs DNA; loss-of-function mutations remove these restraints, contributing to cancer.