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DNA Structure
Double helix with sugar-phosphate backbone.
Semiconservative Replication
DNA replication producing one old and one new strand.
DNA Polymerase
Enzyme synthesizing new DNA strands during replication.
DNA Ligase
Enzyme joining Okazaki fragments on the lagging strand.
Helicase
Enzyme unwinding DNA double helix during replication.
Topoisomerase
Enzyme relieving strain ahead of replication fork.
Leading Strand
Continuously synthesized DNA strand in replication.
Lagging Strand
Discontinuously synthesized DNA strand in replication.
Nucleotide Composition
Sugar, phosphate, and nitrogen base structure.
Nitrogenous Bases
Adenine, thymine, guanine, cytosine in DNA.
Purines
Two-ring nitrogenous bases: adenine and guanine.
Pyrimidines
Single-ring nitrogenous bases: thymine and cytosine.
Base Pairing Rules
A pairs with T; G pairs with C.
Antiparallel Strands
DNA strands oriented in opposite directions.
3' End
End of DNA with hydroxyl group on sugar.
5' End
End of DNA with phosphate group on sugar.
Covalent Bonds
Link nucleotides within a single DNA strand.
Hydrogen Bonds
Hold complementary base pairs together in DNA.
Van der Waals Interactions
Stabilize stacked base pairs in DNA structure.
DNA Sequence
Linear arrangement of nucleotides encoding genetic information.
Transcription
Process converting DNA sequence into mRNA.
Translation
Process synthesizing polypeptides from mRNA sequence.
DNA Packaging
Influences gene expression in eukaryotic chromosomes.
Antiparallel strands
DNA strands run in opposite directions.
5' end
Terminus with a phosphate group attached.
3' end
Terminus with a hydroxyl group attached.
Semiconservative replication
Each daughter DNA has one old strand.
Origins of replication
Sites where DNA replication begins.
Helicase
Enzyme that unwinds the DNA double helix.
Topoisomerase
Relieves strain ahead of the replication fork.
Single-strand binding proteins
Stabilize unwound DNA template strands.
Leading strand
Synthesized continuously in 5' to 3' direction.
Lagging strand
Synthesized discontinuously in segments called Okazaki fragments.
DNA polymerase
Enzyme that catalyzes DNA strand elongation.
RNA primers
Short RNA sequences required to initiate DNA synthesis.
Okazaki fragments
Short DNA segments on the lagging strand.
DNA ligase
Enzyme that joins Okazaki fragments together.
Replication fork
Y-shaped region where DNA is unwound.
Nucleotide pairing
Adenine pairs with thymine; guanine pairs with cytosine.
DNA replication process
Involves unwinding, template synthesis, and joining fragments.
Fragment synthesis
DNA pol III adds nucleotides to 3' end.
Parent cell replication
Process of copying DNA for cell division.
Enzymatic roles in replication
Proteins coordinate to replicate and repair DNA.
Discontinuous replication
Lagging strand synthesis occurs in separate segments.
Replication enzymes
Proteins that facilitate the DNA replication process.
Carbons in nucleotides
Numbered carbons determine DNA strand orientation.
Base Pairing Specificity
A=T and G=C ensure accurate DNA replication.
DNA Polymerase
Enzyme adding nucleotides only at 3' end.
Telomeres
Repetitive sequences capping eukaryotic chromosome ends.
Chromosome
DNA molecule packed with proteins.
Bacterial Chromosome
Single circular DNA molecule with minimal protein.
Eukaryotic Chromosome
Linear DNA molecule with extensive protein association.
Chromatin
DNA-protein complex in eukaryotic cells.
Gene Expression
Process where DNA directs protein synthesis.
Transcription
Synthesis of RNA using DNA as template.
Translation
Production of polypeptides from mRNA.
Central Dogma
Flow of genetic information: DNA→RNA→Protein.
mRNA
Carries genetic message from DNA to ribosomes.
tRNA
Transfers amino acids during protein synthesis.
rRNA
Structural component of ribosomes.
Pre-mRNA
Initial RNA transcript in eukaryotes before processing.
RNA Processing
Modification of pre-mRNA to final mRNA.
Codons
Three-nucleotide sequences on mRNA for amino acids.
Triplet Code
Genetic instructions written as three-nucleotide groups.
Template Strand
DNA strand used for RNA transcription.
HeLa Cells
Cancer cells with active telomerase, rendering them immortal.
One Gene-One Polypeptide Hypothesis
Each gene codes for a specific polypeptide.
Gene Expression Regulation
Control of transcription and translation processes.
Transcription and Translation Simultaneity
Prokaryotes can transcribe and translate simultaneously.
Template Strand
DNA strand used for mRNA synthesis.
Coding Strand
DNA strand with same sequence as mRNA.
mRNA
Messenger RNA, complementary to DNA template.
Codon
mRNA triplet coding for amino acids.
Start Codon
Initiates translation; typically AUG.
Stop Codons
Signals termination of translation; three types.
Genetic Code
Set of rules for translating codons to amino acids.
Redundant Code
Multiple codons can code for the same amino acid.
Reading Frame
Groupings of three nucleotides for translation.
RNA Polymerase
Enzyme that synthesizes RNA from DNA template.
Promoter
DNA sequence where RNA polymerase binds to start transcription.
Terminator
DNA sequence signaling the end of transcription.
Transcription Unit
DNA segment transcribed into RNA molecule.
Transcription Factors
Proteins aiding RNA polymerase binding to promoter.
5' Cap
Modified guanine nucleotide added to mRNA's 5' end.
Poly-A Tail
50 to 250 adenine nucleotides added to mRNA's 3' end.
RNA Splicing
Process of removing introns and joining exons.
Introns
Non-coding regions removed during RNA processing.
Exons
Coding regions retained in mature mRNA.
Spliceosome
Complex that facilitates RNA splicing.
Pre-mRNA
Initial RNA transcript before processing.
5' UTR
Untranslated region at the 5' end of mRNA.
3' UTR
Untranslated region at the 3' end of mRNA.
Introns
Non-coding sections of mRNA removed during splicing.
Exons
Coding sections of mRNA that remain after splicing.
Spliceosome
Complex that splices introns from mRNA.
Small RNAs
RNA molecules aiding in splicing introns.
Ribozyme
RNA that catalyzes biochemical reactions.
Alternative RNA splicing
Process allowing multiple polypeptides from one gene.
Domains
Distinct functional regions within proteins.
tRNA
Transfers amino acids to ribosomes during translation.
