Protein Synthesis: Gene Expression(Transcription/Translation), Regulation of Gene Expression

Intro to Transcription

Promoter

A specific DNA sequence where RNA polymerase binds to initiate transcription.

Terminator

A DNA sequence signaling the end of transcription.

RNA polymerase

The enzyme responsible for polymerizing RNA from a DNA template during transcription without requiring a primer.

Gene

A segment of DNA that includes the promotores, coding sequence, and terminator, encoding a functional product such as a protein.

Upstream

DNA sequences located opposite to the direction of transcription, before the promoter region.

Downstream

DNA sequences located opposite to the direction of transcription, following the coding region.

Coding sequence

The portion of a gene that is transcribed into RNA and ultimately translated into protein.

Transcription

The process of copying a genes DNA sequence into messenger RNA (mRNA).

mRNA

The RNA molecule that carries the genetic information from DNA to the ribosome for protein synthesis.

5’ cap

A modified nucleotide added to the 5’ end of eukaryotic mRNA after transcription, important for mRNA stability and translation.

Steps of Transcription

RNA polymerase

The enzyme responsible for synthesizing RNA by reading the DNA template strand during transcription.

Promoter

A specific DNA sequence where RNA polymerase binds to initiate transcription.

Transcription factors

Proteins in eukaryotic that assist RNA polymerase in binding to the promoter region.

Template strand

The DNA strand that serves as a guide for RNA synthesis during trascription.

Elongation

The step in transcription where RNA polymerase adds RNA nucleotides to extend the RNA molecule in the 5’ to 3’ direction.

Termination

The final step of transcription where RNA polymerase stops RNA synthesis and releases the RNA molecule.

Pre-mRNA

The initial RNA transcript un eukaryotes that requires further RNA processing before becoming mature mRNA.

Terminator sequence

A DNA sequence signaling RNA polymerase to stop transcription.

5’ cap

A modified nucleotide added to the 5’ end of eukaryotic pre-mRNA during RNA processing to protect the RNA and assist in translation.

RNA processing

Modifications such as splicing, addition of the 5’cap, and poly-A tail that convert pre-mRNA into mature mRNA in eukaryotes.

5’ to 3’ direction

The direction in which RNA polymerase synthesizes RNA, adding nucleotides to the 3’ end.

Multiple RNA polymerase

Several RNA polymerase enzymes can transcribe the same gene simultaneously to increase RNA production.

Eukaryotic RNA processing and splicing

Modify premature mRNA to produce mature RNA ready for translation

5’ cap

A modified guanine nucleotide added to the 5’ end of premRNA that protects the RNA and assists in ribosome attachment and nuclear export.

Alternative RNA splicing

A process where a single pre mRNA transcript can be spliced in different ways to produce multiple mature mRNA variants, leading to different proteins.

Exons

Coding regions of DNA and RNA that are expressed and translated into proteins after introns are removed.

Introns

Noncoding, intervening sequences in eukaryotic genes that are removed from pre mRNA during RNA splicing.

Poly-A tail

A sequence of adenine nucleotides added to the 3’ end of pre mRNA that protects RNA from degradation and aids in nuclear export and translation.

Pre mRNA

The initial, premature RNA transcript in eukaryote that contains both introns and extrons and requires processing before translation.

RNA processing

The modification of pre mRNA in eukaryotes, including the addition of the 5’ cap and poly-A tail, to produce mature mRNA.

RNA splicing

The removal of introns joining exons in pre mRNA by the spliceosome to create a continuous coding sequence.

Spliceosome

A large complex of RNA and proteins that catalyzes the removal of introns and ligation of exons during RNA splicing.

Translation

The process by which ribosomes synthesize proteins using the mature mRNA as a template.

Introduction to types of RNA

Distinct RNA molecule that plays specific roles in the process of gene expression and protein synthesis.

mRNA

A type of RNA that carries genetic information from DNA to the ribosome, serving as a template for protein synthesis by containing codons.

rRNA

RNA that forms the structural and functional core of ribosomes, essential for translation but not translated into protein itself.

tRNA

RNA molecules that transport specific amino acids to the ribosome during translation and contain anticodons complementary to mRNA codons.

Codon

A sequence of three nucleotides on mRNA that codes for a specific amino acid during translation,

Anticodon

A three-nucleotide sequence on tRNA that is complementary to the mRNA codon, enabling accurate amino acid placement.

Amino acid

The monomer building blocks of proteins, carried by tRNA to the ribosome for polypeptide assembly.

Translation

The process by which ribosomes synthesize proteins using the sequence encoded in mRNA.

Ribosome

A complex molecular machine composed of rRNA and proteins that facilitates the translation of mRNA into protein.

RNA folding

The process by which single-stranded RNA molecules, like tRNA and rRNA, form complex three-dimensional structures necessary for their function.

Genetic code

The set of rules by which information encoded in mRNA codons is translated into amino acids in proteins.

Genetic code

The universal or nearly universal set of rules that defines how the nucleotide sequence of mRNA is translated into amino acids.

Codon

A sequence of three nucleotides in messenger RNA that specifies a particular amino acid or stop signal during protein synthesis.

mRNA

A type of RNA that carries the genetic information transcribed from DNA to the ribosome for protein synthesis.

Start codon

The specific codon (usually AUG) in mRNA that signals the beginning of translation and codes for methionine.

Stop codon

Codons (such as UAA, AUG, UGA) that do not code for amino acids but signal the termination of protein synthesis.

Transcription

The process of synthesizing mRNA from a DNA template, replacing thymine (T) with uracil (U) in RNA.

Polypeptide chain

A chain of amino acids linked by peptide bonds that folds into a functional protein.

Amino acid

The building blocks of proteins, each specified by one or more codons in the genetic code.

Anticodon

A sequence of three nucleotides in tRNA complementary to a codon in mRNA, ensuring correct amino acid incorporation.

Template strand

The DNA strand used as template during transcription to synthesize mRNA.

Coding strand

The DNA strand whose sequence matches the mRNA sequence (except T is replaced by U in RNA).

Ribosome

A complex molecular machine made of proteins and ribosomal RNA that facilitates the assembly of amino acids into proteins during translation.

tRNA

RNA molecules that carry amino acids to the ribosome and match their anticodons with codons on the mRNA to ensure correct protein synthesis.

Anticodon

A sequence of three nucleotides on a tRNA molecule that pairs complementario with a codon on the mRNA during translation.

Charged tRNA

A tRNA molecule that is covalently attached to its specific amino acid, ready to add it to the growing polypeptide chain.

Discharged tRNA

A tRNA molecule that has released its amino acids and is no longer attached to one.

Small ribosomal subunit

The smaller component of the ribosome that binds to the mRNA and helps decode the message; 30S in prokaryotes and 40S in eukaryotes.

Large ribosomal subunit

The larger component of the ribosome responsible for forming peptide bonds between amino acids; 50S in prokaryotes and 60S in eukaryotes.

70S ribosome

The complete ribosome in prokaryotes, composed of the 50S large and 30S small subunits.

80S ribosome

The complete ribosome in eukaryotes, composed of the 60S large and 40S small subunits.

A site (Aminoacyl site)

The ribosomal binding site where charged tRNAs first enter carrying the next amino acid to be added.

P site (peptidyl)

The ribosomal site that holds the tRNA attached to the growing polypeptide chain.

E site

The ribosomal site where the discharged tRNAs exit after their aminos acid has been added to the chain.

mRNA

The RNA transcript that carries the genetic code from DNA to the ribosome for protein synthesis.

Polypeptide chain

A growing sequence of amino acids linked by peptide bonds that will fold into a functional protein.

Steps of translation

Biological process where ribosomes synthesize proteins by decoding messenger RNA into a polypeptide chain.

5’cap

A modified guanine nucleotide added to the 5’ end of eukaryotic mRNA that helps protects the mRNA and assists in ribosome binding during translation initiation.

Anticodon

A sequence of three nucleotides on a transfer RNA molecule that is complementary to a specific mRNA codon.

Codon

A sequence of three nucleotides on messenger RNA that specifies a particular amino acids into or a stop signal during translation.

Elongation

The stage of translation where amino acids are sequentially added to the growing polypeptide chain at the ribosome.

Initiation factors

Proteins that assist in the assembly of the translation initiation complex, including the small ribosomal subunit, mRNA, and the initiator tRNA.

Large ribosomal subunit

The larger component of the ribosome that joins the small subunit during initiation and catalyzes peptide bond formation during elongation.

Small ribosomal subunit

The smaller component of the ribosome that binds to mRNA and the initiation tRNA during translation initiation.

Start codon

The codon AUG on mRNA that signals the start of translation and codes for methionine.

Stop codon

A codon such as UGA on mRNA that signals termination of translation and does not code for an amino acid.

Termination

The final step of translation where a sto codon triggers release factors to disassemble the translation complex and release the completed polypeptide.

tRNA binding sites

Sites on the ribosome where tRNAs bind during translation: A site for incoming charged tRNA, P site for tRNA holding the growing polypeptide, and E site for discharged tRNA.

Charged tRNA

A tRNA molecule covalently attached to its specific amino acid, ready to participate in translation.

Release factor

A protein that binds to the ribosome at a stop codon to trigger termination of translation.

Energy

Translation required energy, often in the form of GTP, to drive the assembly and movement of the ribosome and tRNAs.

Post translational modification

Refers to the covalent changes made to a protein after its synthesis during translation that regulate its activity, stability, or localization.

Messenger RNA

A type of RNA that carries genetic information from DNA to the ribosome for protein synthesi,

Polypeptide chain

A linear sequence of amino acids linked by peptide bonds that folds into a functional protein.

Methylation

The addition of a methyl group (CH3) to a protein, often affecting gene expression or protein function.

Acetylation

The addition of an acetyl group to a protein, which can influence protein stability and interactions.

Ubiquination

The attachment of ubiquities, a small regulatory protein, to a target protein, often marking it for degradation.

Phosphorylation

The addition of a phosphate group to a protein, commonly regulating enzyme activity and signal transduction.

Hydroxylation

The addition of a hydroxyl group (-OH) to a protein, which can affect protein structure and function.

Lipidation

The covalent attachment of lipid molecules to a protein, aiding in membrane association.

Disulfide bonds

Covalent bonds formed between sulfur atoms of cysteine residues, stabilizing protein structure.

Glycosylation

The addition of carbohydrate groups to proteins, important for protein folding and cell signaling.

Protein kinases

An enzyme that catalyzes phosphorylation by transferring a phosphate group from ATP to a protein.

Differences between Prokaryotes and Eukaryotes in Protein Synthesis

Transcription Prokaryotes

Pribnow Box (-10bp) TATAAT & -35 box

RNA Pol + sigma factor

No mRNA processing