Protein Synthesis: Transcription and Translation

These vocabulary flashcards cover the fundamental concepts of protein synthesis, including transcription, translation, and post-transcriptional modifications.

Central dogma of molecular biology

A set of ideas proposed by Francis Crick in $1956$ stating that information passes from genes ($DNA$ base sequences) to an $RNA$ copy, which then directs protein production at ribosomes.

Transcription

The synthesis of $RNA$ using the base sequence in $DNA$ as a template, occurring in the nucleus of eukaryotic cells.

RNA polymerase

An enzyme that separates $DNA$ strands and links $RNA$ nucleotides by complementary base pairing to form an $RNA$ strand during transcription.

Gene

A specific sequence of nitrogenous bases at a particular location in a $DNA$ molecule that codes for a polypeptide.

Template strand

The single strand of $DNA$ used as a blueprint to create a messenger $RNA$ ($mRNA$) molecule; also known as the antisense strand.

Complementary base pairing (Transcription)

The alignment of $RNA$ nucleotides where adenine ($A$) on $DNA$ pairs with uracil ($U$) on $RNA$, and cytosine ($C$) pairs with guanine ($G$).

Promoter

A non-transcribed sequence of bases near the beginning of a gene that provides a recognition and binding site for $RNA$ polymerase.

Terminator

A sequence of nucleotides that causes $RNA$ polymerase to detach from the $DNA$ and release the newly synthesized $RNA$ transcript.

Point mutation

A change in only one base of a gene that can alter transcription and protein structure, such as the base substitution causing sickle-cell disease.

Messenger RNA (mRNA)

A single-stranded $RNA$ molecule that carries the genetic message from the nucleus to the ribosomes in the cytoplasm.

Translation

The process where the sequence of $mRNA$ nucleotides is decoded to produce a specific sequence of amino acids in a polypeptide.

Transfer RNA (tRNA)

A type of $RNA$ that carries specific amino acids to the ribosome; it contains an anticodon that pairs with an $mRNA$ codon.

Ribosomal RNA (rRNA)

A structural component of ribosomes that combines with proteins to facilitate the synthesis of polypeptides.

Codon

A set of three bases in an $mRNA$ molecule that codes for one of the $20$ different amino acids.

Anticodon

A triplet of bases in a $tRNA$ molecule that is complementary to a specific $mRNA$ codon.

Genetic code universality

The principle that, with minor exceptions, all organisms share the same genetic code, allowing the insertion of genes from one species to another.

Degeneracy

A characteristic of the genetic code where more than one codon can code for the same amino acid.

Introns

Non-coding sections of a primary $mRNA$ transcript that are removed during processing before the molecule leaves the nucleus.

Exons

The segments of $mRNA$ that remain after splicing and form the mature $mRNA$ used for protein synthesis.

Alternative splicing

A process where different combinations of exons from a single gene are joined to produce multiple distinct mature $mRNA$ transcripts and proteins.

A site

The ribosomal binding site that holds the $tRNA$ carrying the next amino acid to be added to the growing polypeptide chain.

P site

The ribosomal binding site that holds the $tRNA$ carrying the growing polypeptide chain.

E site

The ribosomal binding site responsible for discharging the $tRNA$ that has lost its amino acid.

Directionality of synthesis

Transcription and translation both occur in the $5'$ to $3'$ direction.

Ubiquitin

A chemical tag attached to damaged or unneeded proteins to signal their destruction by the cell.

Proteasome

A cellular organelle that degrades marked proteins into free amino acids, which can then be reused in protein synthesis.

Proteome

The entire set of proteins that is or can be expressed by a cell, tissue, or organism at a given time.