BIOL 23373 - General Genetics, Lecture 10: Translation I

Flashcards covering key vocabulary, concepts, and definitions from Lecture 10: Translation I, including the flow of genetic information, parts of the ribosome, and the phases of translation in bacteria and eukaryotes.

Transcription

The synthesis of a single-stranded RNA molecule (transcript) from a DNA template (gene).

mRNA

A type of RNA that specifies the amino acid sequence of a polypeptide (protein).

Translation

The synthesis of a polypeptide using an mRNA template.

Amino Acids

The fundamental units of proteins, forming polymers called polypeptides.

Polypeptides

Polymers of amino acids, also known as proteins.

Peptide Bonds

Chemical bonds that link the amino end of one amino acid to the carboxyl end of another, forming a polypeptide chain.

Codons

Groups of three consecutive nucleotides in an mRNA coding region, each corresponding to a specific amino acid.

Start Codon (AUG)

A specific codon on mRNA that defines the reading frame for translation and initiates polypeptide synthesis, corresponding to methionine.

Genetic Code

The set of rules by which information encoded in mRNA nucleotide sequences is translated into amino acid sequences in polypeptides. It contains 64 different codons.

Stop Codons

Three specific codons (UAA, UAG, UGA) in the genetic code that signal the termination of translation and do not specify an amino acid.

Synonymous Codons

Different codons that specify the same amino acid, contributing to the redundancy of the genetic code.

Degeneracy

The redundancy in the genetic code, meaning that most amino acids are specified by more than one codon, often differing only in the third base.

Universal Genetic Code

The principle that the genetic code is nearly identical in all organisms, with few exceptions mainly found in mitochondria.

tRNAs (Transfer RNAs)

Adaptor molecules in translation that interpret and act on information in mRNA by carrying specific amino acids to the ribosome.

Anticodon

A three-nucleotide sequence on a tRNA molecule that is complementary and antiparallel to an mRNA codon, enabling specific amino acid delivery.

tRNA Structure

A characteristic cloverleaf structure in two dimensions, featuring an acceptor stem for amino acid binding and an anticodon loop.

Iso-accepting tRNAs

Different tRNA molecules that have different anticodons but carry the same amino acid.

Third-Base Wobble

A relaxation of complementary base-pairing rules at the third codon position (3' end of codon and 5' end of anticodon), allowing one tRNA to pair with more than one synonymous codon.

Charged tRNAs

tRNA molecules that have a specific amino acid attached to their acceptor stem.

Uncharged tRNAs

tRNA molecules that do not have an amino acid attached.

Aminoacyl-tRNA Synthetases

A family of 20 enzymes (one for each amino acid) that catalyze the correct attachment of an amino acid to its corresponding tRNA molecule.

Ribosomes

Complex molecular machines composed of ribosomal RNAs (rRNAs) and proteins, responsible for assembling amino acids into polypeptides during translation.

Ribosomal Subunits

The large and small components of a ribosome, measured in Svedberg units (S), which come together to form a functional ribosome.

Aminoacyl Site (A site)

A binding site on the ribosome that holds the tRNA containing the next amino acid to be added to the growing polypeptide chain.

Peptidyl Site (P site)

A binding site on the ribosome that holds the tRNA to which the nascent polypeptide chain is attached.

Exit Site (E site)

A binding site on the ribosome that provides an avenue for uncharged tRNA molecules to exit after their amino acid has been transferred to the polypeptide.

Polypeptide Channel

A channel within the ribosome through which the newly synthesized polypeptide chain emerges during translation.

Phases of Translation

The three main stages of polypeptide synthesis: Initiation, Elongation, and Termination.

IF3 (Initiation Factor 3)

A bacterial initiation factor that prevents the small ribosomal subunit from binding prematurely to the large ribosomal subunit.

Preinitiation Complex (Bacteria)

A complex formed in bacteria when the small (30S) ribosomal subunit's 16S rRNA pairs with the Shine-Dalgarno sequence on the mRNA.

Shine-Dalgarno Sequence

A purine-rich consensus sequence (AG rich) in bacterial mRNA, located 3-9 nucleotides upstream of the start codon, that helps position the start codon in the P site by pairing with the 16S rRNA.

Initiator tRNA (Bacteria)

The specific tRNA that binds to the start codon in bacteria, carrying the modified amino acid N-formylmethionine (fMet).

N-formylmethionine (fMet)

The modified amino acid carried by the initiator tRNA in bacteria, signaling the start of a polypeptide chain.

30S Initiation Complex (Bacteria)

A complex formed in bacterial translation initiation, consisting of the 30S ribosomal subunit, mRNA, initiator tRNA, IF1, IF2, and GTP.

70S Initiation Complex (Bacteria)

The fully assembled bacterial ribosome, formed when the large (50S) ribosomal subunit joins the 30S initiation complex.

eIF Proteins (Eukaryotic Initiation Factors)

A group of proteins that facilitate the process of translation initiation in eukaryotes.

Preinitiation Complex (Eukaryotes)

A complex formed in eukaryotes consisting of the small (40S) ribosomal subunit, eIF proteins, and a charged tRNAmet.

Initiation Complex (Eukaryotes)

The complex formed when the eukaryotic preinitiation complex joins eIF4 proteins at the 5' cap of mRNA, which then scans for the start codon.

Kozak Sequence

A consensus sequence (5'-ACCAUGG-3') in eukaryotic mRNA where the start codon (AUG) is typically embedded, aiding in its recognition during initiation.