Keywords

Template

The DNA strand that serves as a guide for the synthesis of a new complementary DNA strand during replication.

Origin of replication

Specific sequence on the DNA where replication begins.

DNA polymerase

Enzyme responsible for synthesizing new DNA strands by adding nucleotides to the growing DNA chain during replication.

dATP, dGTP, dCTP, dTTP

Deoxyribonucleotides that serve as building blocks for DNA synthesis, representing the bases adenine, guanine, cytosine, and thymine, respectively.

Proofreading

Mechanism by which DNA polymerase detects and corrects errors in nucleotide incorporation during DNA replication.

Helicase

Enzyme responsible for unwinding the DNA double helix ahead of the replication fork.

Primase

Enzyme that synthesizes short RNA primers to initiate DNA replication.

Primer

Short RNA or DNA sequence that serves as a starting point for DNA synthesis by DNA polymerase.

Replication fork

Y-shaped structure formed during DNA replication where the parental DNA strands are unwound and new strands are synthesized.

Leading strand

The DNA strand that is synthesized continuously in the 5' to 3' direction at the replication fork.

Lagging strand

The DNA strand that is synthesized discontinuously in short fragments called Okazaki fragments at the replication fork.

End replication problem

The challenge of replicating the ends of linear DNA molecules, which leads to the shortening of DNA after each round of replication.

Telomere

Protective structure at the ends of linear chromosomes that helps prevent the loss of genetic information during DNA replication.

Telomerase

Enzyme that adds repetitive DNA sequences to telomeres, counteracting the shortening of telomeres during DNA replication.

Equilibrium density gradient centrifugation

A technique used to separate DNA fragments based on their density in a density gradient.

Transcription

The process by which genetic information encoded in DNA is copied into RNA by RNA polymerase.

Ribonucleic acid, RNA

A nucleic acid molecule that plays a crucial role in gene expression, including mRNA, tRNA, and rRNA.

Uracil, U

One of the four RNA nucleotides, which pairs with adenine during transcription, replacing thymine found in DNA.

Ribozyme

RNA molecules with enzymatic activity, capable of catalyzing specific biochemical reactions.

Ribosomal RNA, rRNA

RNA component of the ribosome that plays a key role in protein synthesis.

Messenger RNA, mRNA

RNA molecule transcribed from DNA that carries genetic information from the nucleus to the cytoplasm for protein synthesis.

Transfer RNA, tRNA

RNA molecule that delivers specific amino acids to the ribosome during protein synthesis.

RNA polymerase

Enzyme responsible for synthesizing RNA from a DNA template during transcription.

Transcription unit

The segment of DNA that is transcribed into a single RNA molecule.

Promoter

DNA sequence where RNA polymerase binds to initiate transcription.

Terminator

DNA sequence that signals the end of transcription.

Upstream

Refers to the DNA sequence in the 5' direction of a gene or a specific site.

Downstream

Refers to the DNA sequence in the 3' direction of a gene or a specific site.

Hairpin

Secondary structure formed by a single-stranded nucleic acid molecule that folds back on itself.

Inverted repeats

DNA sequences with inverted complementary repeats that can form hairpin structures.

Stem

The double-stranded region of a hairpin or other secondary structures in nucleic acids.

Loop

The single-stranded region of a hairpin or other secondary structures in nucleic acids.

Rho factor

Protein involved in transcription termination in prokaryotes.

RNA polymerase I, II, III

Different types of RNA polymerases responsible for transcribing different classes of RNA in eukaryotic cells.

Transcription factor

Proteins that assist RNA polymerase in binding to DNA for transcription initiation.

Enhancer

DNA sequence that can increase the transcription of a gene.

TATA box

DNA sequence found in the promoter region of genes; essential for transcription initiation.

TATA-binding protein (TBP)

Protein that binds to the TATA box and plays a role in transcription initiation.

Primary transcript

The initial RNA transcript synthesized from a gene before any modifications.

Mature RNA

The final processed RNA molecule after all modifications, ready to be translated into protein.

Denaturation

The separation of the double-stranded DNA or RNA into single strands by breaking the hydrogen bonds between the base pairs.

Melting

The process of denaturation where the hydrogen bonds holding the two strands of DNA or RNA together are disrupted.

Renaturation

The process of reassociating complementary single-stranded DNA or RNA molecules to form double-stranded structures.

Reannealing

Another term for the reassociation of complementary single-stranded DNA or RNA molecules.

Hybridization

The process of forming a double-stranded nucleic acid molecule by complementary base pairing between two single strands from different sources.

Exon

The coding region of a gene that is expressed in the mature mRNA.

Intron

Non-coding intervening sequences within a gene that are removed during RNA splicing.

Splicing

The process of removing introns and joining exons in pre-mRNA to produce mature mRNA.

5’ cap

A modified guanine nucleotide added to the 5' end of eukaryotic mRNA, playing a role in mRNA stability and translation initiation.

polyA tail

A string of adenine nucleotides added to the 3' end of eukaryotic mRNA, involved in mRNA stability and export from the nucleus.

polyadenylation

The process of adding a polyA tail to the 3' end of mRNA.

Small nuclear RNA, snRNA

RNA molecules involved in RNA splicing and processing.

Small nuclear ribonucleoprotein particle, snRNP

Complexes of snRNA and protein that form the spliceosome.

5’ splice site

The site at the 5' end of an intron where splicing occurs.

3’ splice site

The site at the 3' end of an intron where splicing occurs.

Branch point

A specific adenosine residue within the intron that participates in forming the lariat structure during splicing.

Lariat

The looped structure formed during splicing when the intron is removed.

Spliceosome

Complex of snRNPs and proteins that catalyze RNA splicing.

Self-splicing introns

Introns that can catalyze their removal without the aid of a spliceosome.

Alternative splicing

The process by which different combinations of exons within a single gene can be spliced together to generate diverse mRNA transcripts.

Small nucleolar RNA, snoRNA

RNA molecules involved in the processing and modification of ribosomal RNA.

Amino acid

The building blocks of proteins, consisting of an amino group, a carboxyl group, and a side chain.

Peptide bond

The covalent bond formed between the amino group of one amino acid and the carboxyl group of another during protein synthesis.

Protein

Large biomolecules composed of amino acids that perform a wide range of functions in living organisms.

Polypeptide

A chain of amino acids linked by peptide bonds, forming a protein.

Alpha helix

A common secondary structure in proteins where the polypeptide chain forms a right-handed coil stabilized by hydrogen bonds.

Beta pleated sheet

Another common secondary structure in proteins where the polypeptide chain forms a sheet-like structure stabilized by hydrogen bonds.

Triplet

A sequence of three nucleotides in mRNA that codes for a specific amino acid.

Codon

A three-nucleotide sequence in mRNA that specifies a particular amino acid during protein synthesis.

Genetic code

The set of rules that dictate the translation of nucleotide sequences in mRNA into amino acids during protein synthesis.

Degenerate code

Refers to the redundancy in the genetic code where multiple codons can code for the same amino acid.

Anticodon

A sequence of three nucleotides in tRNA that is complementary to a codon in mRNA during translation.

Wobble

Base pairing flexibility at the third position of the codon-anticodon interaction, allowing some tRNAs to bind to multiple codons.

Stop codon / nonsense codon

A codon in mRNA that signals the termination of protein synthesis, such as UAA, UAG, or UGA.

Initiation codon

The codon (usually AUG) that initiates protein synthesis and establishes the reading frame.

Synonymous codons

Codons that specify the same amino acid.

Isoaccepting tRNAs

tRNA molecules that have different anticodons but can still bind to the same amino acid.

Aminoacyl-tRNA

A tRNA molecule covalently linked to its corresponding amino acid.

Aminoacyl-tRNA synthetase

Enzyme responsible for attaching the correct amino acid to its corresponding tRNA molecule during protein synthesis.

5’ untranslated region, 5’ UTR

The region at the 5' end of an mRNA molecule that is not translated into protein but may contain regulatory sequences.

3’ untranslated region, 3’ UTR

The region at the 3' end of an mRNA molecule that is not translated into protein but may contain regulatory sequences.

Ribosome

Complex cellular machinery responsible for protein synthesis by translating mRNA into a polypeptide chain.

Initiator tRNA

The tRNA molecule that carries the amino acid methionine and initiates protein synthesis at the start codon (AUG).

A site

The site on the ribosome where incoming aminoacyl-tRNAs bind during translation.

P site

The site on the ribosome where the peptidyl-tRNA binds and the growing polypeptide chain is elongated during translation.

E site

The site on the ribosome where discharged tRNAs exit after releasing their amino acids.

Peptidyl transferase

The ribozyme activity of the ribosome responsible for catalyzing peptide bond formation during protein synthesis.

Shine-Dalgarno sequence

The ribosomal binding site in prokaryotic mRNA that helps position the ribosome for translation initiation.

Kozak sequence

The consensus sequence in eukaryotic mRNA that surrounds the AUG start codon and helps initiate translation.

Scanning

The process by which the ribosome searches for the start codon in eukaryotic mRNA during translation initiation.

Reading frame

The correct grouping of nucleotides into codons during translation to ensure the proper sequence of amino acids in the resulting protein.

Open reading frame

A continuous stretch of nucleotides that can be translated into a protein without encountering a stop codon.

In frame

Refers to the correct alignment of codons in mRNA during translation that maintains the reading frame for protein synthesis.

Out of frame

Refers to a shifted alignment of codons in mRNA during translation that disrupts the reading frame and leads to incorrect protein synthesis.

Structural gene

This refers to a gene that encodes a protein. It provides the necessary information to synthesize a functional product, which could be an enzyme, a structural component of a cell, or a regulatory protein.

Regulatory gene

Regulatory genes control the expression of other genes. They encode proteins (like transcription factors) that bind to specific DNA sequences and either activate or repress the transcription of target genes.

Regulatory sequences

These are specific DNA sequences that are recognized by regulatory proteins. They are involved in controlling the expression of genes by serving as binding sites for regulatory proteins.

Protein domain

A protein domain is a distinct functional or structural unit within a protein. Proteins can have multiple domains, each contributing to specific functions such as binding to DNA or other proteins.

Activator

An activator is a protein that enhances gene transcription by binding to specific DNA sequences and promoting the assembly of the transcription machinery at the gene's promoter.

Repressor

A repressor is a protein that inhibits gene transcription by binding to DNA sequences and blocking the assembly of the transcription machinery or by recruiting factors that prevent transcription.