The Central Dogma of Molecular Biology and Cell Cycle

Vocabulary practice flashcards covering DNA structure, transcription, translation, replication, mutations, and the cell cycle based on lecture slides.

Central Dogma of Molecular Biology

The core framework describing the flow of genetic information in a biological system from DNA to RNA and protein.

Major Groove

A structural region of the DNA double helix that exposes nucleotides and facilitates the binding of transcription factors, polymerases, and nucleases.

Minor Groove

A structural region of the DNA double helix that binds antibiotics and dyes or stains.

Law of Complementary Base Pairing

A lock and key principle in DNA and RNA where a purine binds a specific pyrimidine through hydrogen bonding.

Antiparallel Strands

Strands of DNA running in opposite directions ($5' \rightarrow 3'$ and $3' \rightarrow 5'$), named based on the carbon atoms on the sugar backbone.

Chromatin

A complex of DNA, protein, and RNA that PACKAGES DNA into a small volume, REINFORCE DNA for mitosis, PREVENTS DNA damage, and CONTROLS gene expression.

Nucleosome

A fundamental unit of chromatin structure consisting of DNA wrapped around a protein octamer composed of histones.

Enhancer

A distal DNA regulatory element that binds activator proteins to stimulate chromatin remodeling and initiate transcription.

Promoter Region

A DNA sequence that binds RNA Polymerase and contains a TATA box ($\text{TATAAA}$) where DNA unwinding occurs.

Exon

A sequence of DNA that is retained in mature pre-mRNA and eventually becomes part of a functional protein.

Intron

A non-coding sequence of DNA that is excised from the primary transcript during RNA processing.

Decondensed Chromatin

An open state of chromatin required for transcription to occur, promoted by DNA demethylation, histone acetylation by HATs, and histone demethylation.

Mediator

A protein complex bound by activators that triggers the assembly of RNA Polymerase and general transcription factors at the promoter site.

Template Strand

The $3' \rightarrow 5'$ DNA strand read by RNA Polymerase during transcription elongation.

Coding Strand

The $5' \rightarrow 3'$ DNA strand that shares the same sequence as the pre-mRNA transcript, except with thymine instead of uracil.

Pyrophosphate ($\text{PP}_i$)

A byproduct released during synthesis reactions when nucleotide triphosphates (NTPs) are incorporated into RNA.

Poly-A Signal Sequence

A specific sequence that directs RNA Polymerase to terminate transcription and detach from the DNA molecule.

5' Cap and Poly-A Tail

Structural additions made to RNA during processing that regulate nuclear export, prevent degradation, and promote translation.

Alternative Splicing

A regulatory mechanism that allows a single gene to code for multiple proteins by selectively including or excluding different exons in mRNA.

Ribosome

A complex composed of protein and ribosomal RNA that acts as a ribozyme to form peptide bonds during translation, featuring A, P, and E binding sites.

Transfer RNA (tRNA)

An RNA molecule carrying a specific amino acid and featuring an anticodon that hydrogen bonds to an mRNA codon.

Triplet Codon

A three-nucleotide sequence in mRNA or tRNA that specifies a single amino acid.

Degeneracy

The property of the genetic code in which multiple distinct triplet codons code for the same amino acid.

Cap-Dependent Translation Initiation

Translation initiation involving a $43\text{S}$ pre-initiation complex scanning the mRNA from the $5'$ cap to locate the AUG start codon.

Cap-Independent Translation Initiation

Translation initiation where protein complexes bind directly to the start site without scanning, typically occurring under cellular stress.

P Site (Peptidyl Site)

The ribosomal site initially occupied by initiator tRNA bound to methionine during translation initiation.

A Site (Aminoacyl Site)

The ribosomal site where a new incoming aminoacyl-tRNA enters to pair with the mRNA codon.

E Site (Exit Site)

The ribosomal site where uncharged tRNAs relocate before exiting the ribosome.

Peptide Bond

A chemical bond formed between amino acids via a dehydration synthesis reaction releasing $\text{H}_2\text{O}$.

Termination Factor

A protein (such as eRF1) that binds to a stop codon at the ribosome's A site, leading to the release of the protein and dissociation of RNA.

Post-Translational Modification (PTM)

Covalent structural additions to proteins after synthesis, such as acetylation, methylation, phosphorylation, sulfation, and glycosylation.

Replication Origins

AT-rich DNA regions where replication starts, forming replication bubbles with forks at both ends.

Origin Recognition Complex (ORC)

A hexameric protein complex that recognizes and binds the replication origin during pre-replication complex assembly.

Minichromosome Maintenance Complex (MCM)

A complex with helicase activity responsible for unwinding DNA during replication.

Replisome

A molecular machine at each replication fork containing MCMs, GINS, Cdc45, and DNA Polymerases.

Leading Strand

The newly synthesized DNA strand that is synthesized continuously in the $5' \rightarrow 3'$ direction toward the replication fork.

Lagging Strand

The newly synthesized DNA strand synthesized discontinuously in Okazaki fragments away from the replication fork.

Primase

An enzyme that lays down short RNA primers needed for DNA Polymerase to begin synthesis on the lagging strand.

Telomerase

An enzyme containing an RNA template that adds repetitive sequences to chromosome ends to fill gaps left by lagging strand replication.

Germline Mutation

A genetic mutation occurring in gametes that can be passed on to offspring and affects all cells of the organism.

Somatic Mutation

A genetic mutation occurring in non-germline body cells that affects only the individual and is not inherited by offspring.

Spontaneous Mutation

A genetic alteration that arises naturally due to uncorrected errors during normal DNA replication.

Induced Mutation

A genetic alteration caused by exposure to external environmental mutagens, such as radiation or chemical agents.

Insertion Mutation

A type of mutation resulting from the addition of one or more base pairs into a DNA sequence.

Deletion Mutation

A type of mutation resulting from the removal of one or more base pairs from a DNA sequence.

G1 Phase (Gap 1)

The cell cycle phase where the cell accumulates materials for replication, doubles organelles, and carries out primary growth and metabolism.

G0 Phase (Resting Phase)

A state entered by faulty or terminally differentiated cells that permanently or temporarily cease division.

S Phase (Synthesis Phase)

The stage of interphase during which nuclear DNA is replicated and centrioles are duplicated.

G2 Phase (Gap 2)

The stage of interphase where centriole duplication completes and cell division control proteins are produced.

M Phase (Mitosis)

The cell cycle phase during which nuclear division and cytokinesis divide a cell into two identical daughter cells.

Cell Cycle Checkpoints

Surveillance mechanisms (G1, S, G2, and M) that halt cell cycle progression if DNA damage or incomplete replication/assembly is detected.

Cyclin and Cyclin-Dependent Kinase (CDK)

Protein complexes that regulate key steps of the cell cycle, including replication initiation in G1, preventing re-replication in S, and M phase entry in G2.

Prophase

The initial mitotic stage where chromatin condenses into chromosomes, centrosomes move apart, and the mitotic spindle forms.

Metaphase

The mitotic stage where sister chromatids align along the metaphase plate in the middle of the cell.

Anaphase

The mitotic stage where sister chromatids separate and are pulled to opposite spindle poles.

Telophase

The final stage of nuclear division where nuclear membranes reform, chromosomes decondense, and spindle fibers disassemble.

Cytokinesis

The division of the cell cytoplasm into two separate daughter cells following nuclear division.

Kinetochore

A protein structure located on the centromere of each chromosome that serves as the attachment point for spindle microtubules.

Anaphase Promoting Complex (APC)

A protein complex activated during metaphase when microtubules are attached to kinetochores, triggering sister chromatid separation.

Contractile Ring

A ring of actin and myosin filaments that pinches the cell membrane inward to create the cleavage furrow during cytokinesis.