Chapter 14: Gene Expression: From Gene to Protein

This set of vocabulary flashcards covers the fundamental principles of gene expression, including transcription, translation, RNA processing, the genetic code, and the impact of various types of mutations based on the Chapter 14 lecture transcript.

Gene Expression

The multi-step process by which DNA directs the synthesis of proteins or, in some cases, RNA molecules.

Transcription

The DNA-directed synthesis of RNA, where information in DNA is used to produce a complementary messenger RNA ($mRNA$) molecule.

Translation

The RNA-directed synthesis of a polypeptide, using information contained in $mRNA$ to assemble amino acids at ribosomes.

Archibald Garrod

A British physician who in 1902 suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions.

One Gene–One Enzyme Hypothesis

The idea, supported by Beadle and Tatum's study of bread mold, that genes dictate the production of specific enzymes involved in metabolic pathways.

Central Dogma

The concept defined as the cellular chain of command describing the flow of genetic information from DNA to RNA to protein.

Codons

Nonoverlapping, $3$-nucleotide words of $mRNA$ that are translated into specific amino acids to form a polypeptide chain.

Template Strand

The specific DNA strand that provides the sequence of complementary nucleotides for an RNA transcript during transcription.

Coding Strand

The nontemplate DNA strand, which contains a sequence identical to the RNA transcript (except for the replacement of T with U).

RNA Polymerase

An enzyme that separates DNA strands and joins complementary RNA nucleotides in the $5'$ to $3'$ direction without requiring a primer.

Promoter

The specific DNA sequence where RNA polymerase attaches and marks the site where transcription begins.

TATA box

A crucial promoter DNA sequence in eukaryotes involved in forming the transcription initiation complex.

Primary Transcript

The initial, unprocessed RNA transcript produced from any gene, also referred to as Pre-mRNA in eukaryotes.

$5'$ Cap

A modified G nucleotide added to the $5'$ end of a pre-mRNA molecule to facilitate export and protect the transcript.

$3'$ Poly-A Tail

A sequence of adenine nucleotides added to the $3'$ end of eukaryotic pre-mRNA to help ribosomes attach and prevent degradation.

RNA Splicing

The process of removing noncoding regions (introns) from a primary transcript and joining the remaining coding regions (exons).

Introns

Noncoding, intervening sequences within a gene that are removed from the RNA molecule during splicing.

Exons

The segments of an RNA transcript that remain after splicing and are eventually translated into amino acid sequences.

Spliceosomes

Large complexes consisting of proteins and small RNAs that carry out the process of RNA splicing.

Ribozymes

RNA molecules that possess catalytic properties, allowing them to function as enzymes during processes like splicing.

tRNA (Transfer RNA)

An RNA molecule that carries a specific amino acid to the ribosome and has an anticodon to base-pair with a complementary $mRNA$ codon.

Anticodon

A specific nucleotide triplet on a tRNA molecule that base-pairs with a complementary codon on an $mRNA$ strand.

Aminoacyl-tRNA Synthetase

An enzyme responsible for correctly matching a specific tRNA with its corresponding amino acid.

Wobble

Flexible base-pairing at the third position of an $mRNA$ codon, allowing a single tRNA to bind to multiple codons.

P Site

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

A Site

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

E Site

The exit site on a ribosome where discharged tRNAs leave the complex.

Polyribosomes (Polysomes)

Strings of multiple ribosomes translating a single $mRNA$ molecule simultaneously to produce polypeptides quickly.

Signal-Recognition Particle (SRP)

A protein-RNA complex that recognizes a signal peptide and escorts the ribosome to a receptor in the ER membrane.

Point Mutations

Changes in the genetic material of a cell that involve a single nucleotide pair.

Silent Mutations

Nucleotide-pair substitutions that result in no change to the amino acid sequence due to the redundancy of the genetic code.

Missense Mutations

Substitutions that change one amino acid in a protein sequence to a different amino acid.

Nonsense Mutations

Mutations that change an amino acid codon into a stop codon, typically resulting in a nonfunctional, truncated protein.

Frameshift Mutation

An insertion or deletion of nucleotides that shifts the reading frame of the genetic message.

Mutagens

Physical or chemical agents, such as carcinogens, that can cause changes in the DNA sequence.