Molecular Biology and Cellular Processes – Vocabulary Review

A comprehensive set of vocabulary flashcards covering the major terms, structures, enzymes, pathways, and techniques discussed in the Molecular Biology and Cellular Processes lecture.

Cell Cycle

Ordered series of events (G1, S, G2, M) that governs cell growth and division.

G1 Phase

Gap-1 stage (≈9 h) where cell receives growth signals and prepares for DNA synthesis.

S Phase

Synthesis stage (≈10 h) in which every chromosome is replicated, producing sister chromatids; centrioles also duplicate.

G2 Phase

Gap-2 stage (≈4 h) of continued growth and protein production before mitosis.

M Phase (Mitosis)

Stage (≈1 h) where chromosomes and cytoplasm are partitioned into two daughter cells.

Interphase

Collective term for G1, S, and G2 phases between mitoses.

Cyclins

Regulatory proteins whose timed synthesis and proteasomal degradation drive cell-cycle transitions.

Cyclin-Dependent Kinases (CDKs)

Serine/threonine kinases that, when bound to cyclins, phosphorylate targets to propel the cell cycle.

G1/S Checkpoint

Control point that halts cycle if DNA damage is detected; p53-dependent.

G2/M Checkpoint

Checkpoint just before mitosis that verifies quality of DNA replication.

Metaphase-Anaphase Checkpoint

Ensures all chromosomes are aligned and attached to spindle before chromatid separation.

Prophase

Mitotic stage where chromatin condenses and the mitotic spindle begins to form.

Prometaphase

Stage characterized by further chromosome condensation and nuclear envelope breakdown.

Metaphase

Mitotic stage in which chromosomes align on the metaphase plate.

Anaphase

Shortest mitotic stage; sister chromatids separate and move to opposite poles.

Telophase

Stage where chromatids reach poles, nuclear membranes reform, and chromosomes decondense.

Cytokinesis

Division of the cytoplasm, usually concurrent with telophase, forming two cells.

DNA (Deoxyribonucleic Acid)

Double-stranded polymer of nucleotides that stores genetic information.

Nucleotide

DNA monomer consisting of deoxyribose, phosphate, and a nitrogenous base (A, T, G, or C).

Complementary Base Pairing

Specific hydrogen bonding: A–T (2 bonds) and G–C (3 bonds).

Semi-conservative Replication

DNA replication producing molecules with one parental and one newly synthesized strand.

Replication Fork

Y-shaped region where parental DNA unwinds and strands are copied.

Leading Strand

DNA strand synthesized continuously in the 5′→3′ direction.

Lagging Strand

Strand synthesized discontinuously as Okazaki fragments in the 5′→3′ direction.

Okazaki Fragment

Short DNA segment produced on the lagging strand and later joined by ligase.

Helicase

Enzyme that unwinds double-stranded DNA by breaking hydrogen bonds.

Single-Stranded DNA Binding Protein

Protein that stabilizes separated DNA strands during replication.

Topoisomerase

Enzyme preventing supercoiling by cleaving and rejoining DNA strands ahead of the fork.

Primase

RNA polymerase that lays down short RNA primers for DNA polymerase initiation.

DNA Polymerase

Enzyme that extends DNA strands 5′→3′ and proofreads via 3′→5′ exonuclease activity.

DNA Ligase

Enzyme that seals nicks and joins Okazaki fragments on the lagging strand.

Central Dogma

Flow of genetic information: DNA → RNA → Protein.

RNA

Single-stranded nucleic acid with ribose sugar and uracil in place of thymine.

RNA Polymerase I

Nuclear enzyme that synthesizes rRNA.

RNA Polymerase II

Enzyme that transcribes mRNA and some snRNA genes.

RNA Polymerase III

Enzyme responsible for tRNA and small RNA synthesis.

Promoter

DNA sequence where transcription factors and RNA polymerase assemble to begin transcription.

Transcription Factor

Protein that binds specific DNA sequences to regulate transcription initiation.

Enhancer

Distal DNA element binding activator proteins to increase transcription via DNA looping.

Silencer

DNA element that recruits repressor factors to decrease transcription.

mRNA (Messenger RNA)

RNA copy of a gene that serves as template for protein synthesis.

tRNA (Transfer RNA)

Adaptor RNA that carries specific amino acids to the ribosome during translation.

rRNA (Ribosomal RNA)

Structural and catalytic RNA component of ribosomes.

snRNA (Small Nuclear RNA)

RNA involved in splicing pre-mRNA within spliceosomes.

snoRNA (Small Nucleolar RNA)

RNA guiding chemical modification and processing of rRNA in the nucleolus.

miRNA (MicroRNA)

Small non-coding RNA that post-transcriptionally regulates gene expression.

5′ Cap

7-methylguanosine added to mRNA 5′ end for stability and ribosome binding.

Polyadenylation

Addition of 20–250 adenine nucleotides to the 3′ end of mRNA, influencing half-life.

Splicing

Removal of introns from pre-mRNA, joining exons to form mature mRNA.

Alternative Splicing

Process generating multiple mRNA variants from one gene by selective exon inclusion.

Codon

Three-nucleotide sequence on mRNA specifying an amino acid or stop signal.

Start Codon

AUG triplet that initiates translation and encodes methionine.

Stop Codon

UAA, UAG, or UGA; signals termination of translation.

Degenerate Genetic Code

Characteristic whereby most amino acids are specified by more than one codon.

Ribosome

Ribonucleoprotein complex (40S + 60S in eukaryotes) that translates mRNA into protein.

Peptidyl Transferase

Ribozyme activity within rRNA that forms peptide bonds during elongation.

Ubiquitination

Covalent attachment of ubiquitin to lysine residues of target proteins, marking them for degradation.

Proteasome

26S multicatalytic complex that degrades polyubiquitinated proteins into peptides.

Autophagy

Lysosome-mediated degradation pathway for large cytoplasmic contents and organelles.

G Protein-Coupled Receptor (GPCR)

Seven-pass membrane protein that activates heterotrimeric G proteins upon ligand binding.

Receptor Tyrosine Kinase (RTK)

Single-pass receptor whose dimerization activates intrinsic tyrosine kinase activity.

Ras/MAPK Pathway

RTK-linked kinase cascade (RAS→RAF→MEK→ERK) regulating gene expression and proliferation.

PI3K/AKT Pathway

Signal transduction route activating AKT to promote survival and growth.

WNT/β-catenin Pathway

Signalling cascade controlling development and bone remodeling; dysregulated in cancer and arthritis.

Adaptor Protein

Small, multi-domain protein linking two signalling molecules without catalytic activity.

Desmosome

Cell-cell junction that connects intermediate filaments, providing mechanical strength.

Adherens Junction

Cadherin-based cell-cell adhesion linking actin filaments between neighbouring cells.

Cadherin

Calcium-dependent transmembrane adhesion protein binding identical cadherins on adjacent cells.

Necrosis

Accidental cell death due to physical or chemical injury, causing inflammation.

Apoptosis

Programmed cell death essential for development and tissue homeostasis.

Intrinsic Pathway (Apoptosis)

Mitochondria-mediated apoptotic route triggered by cellular stress and BAX/BAK pores.

BCL2 Family

Group of proteins (pro- and anti-apoptotic) regulating mitochondrial outer-membrane permeabilization.

Stem Cell

Cell capable of self-renewal and producing differentiated progeny.

Asymmetric Cell Division

Division producing two daughter cells with different fates, maintaining stem-cell pools.

Fluorescence In Situ Hybridisation (FISH)

Cytogenetic technique using fluorescent probes to detect specific DNA sequences on chromosomes.

Polymerase Chain Reaction (PCR)

In vitro method that exponentially amplifies defined DNA segments via cycles of denaturation, annealing, and extension.

Reverse Transcription PCR (RT-PCR)

Technique converting RNA into cDNA followed by PCR amplification to detect RNA expression.

SDS-PAGE

Gel electrophoresis method separating proteins by molecular mass using SDS detergent.

Isoelectric Focusing (IEF)

Protein separation technique based on migration to their isoelectric point within a pH gradient.

Recombinant Protein Technology

Use of cloning vectors to express genes and produce proteins in host cells.