Unit 4: Gene Expression, Protein Synthesis, and Mutations

Vocabulary flashcards covering Unit 4: Gene Expression, including transcription, translation, nucleic acid differences, mRNA processing, and gene mutations.

Transcription

The first stage of protein synthesis in which the genetic instructions from DNA are transferred into a complementary single-stranded messenger RNA (mRNA) molecule by RNA polymerase so it can leave the nucleus.

Translation

The second stage of protein synthesis occurring at the ribosome, where transfer RNA (tRNA) decodes the message carried by mRNA three bases at a time and delivers amino acids to build a protein.

mRNA (Messenger RNA)

A single-stranded RNA molecule transcribed in the nucleus that copies instructions from DNA and transports them to the ribosome in the cytoplasm.

tRNA (Transfer RNA)

An RNA molecule that carries a specific amino acid to the ribosome and contains a complementary triplet anticodon that binds to an mRNA codon.

rRNA (Ribosomal RNA)

A structural component of ribosomes that aids in matching mRNA codons with tRNA anticodons during translation.

Codon

A series of three consecutive mRNA bases that codes for a specific amino acid or a stop signal.

Anticodon

A triplet of nucleotides on a tRNA molecule that is complementary to a corresponding three-base codon on an mRNA strand.

Amino Acid

The monomer and building block of proteins, transported by tRNA and linked by peptide bonds at the ribosome.

Polypeptide (Protein)

A chain of amino acids joined together by peptide bonds that folds into a specific conformation to carry out cellular functions and express traits.

RNA Polymerase

An enzyme that unzips the DNA double helix and assembles complementary RNA nucleotides into a single strand of mRNA using one DNA strand as a template.

Nucleic Acid

An essential biomolecule, such as DNA or RNA, composed of nucleotide polymers that stores and transmits genetic information.

Nucleotide

The fundamental monomer of nucleic acids, consisting of a 5-carbon sugar (deoxyribose or ribose), a phosphate group, and a nitrogenous base.

Protein Synthesis

A regulated two-stage cellular mechanism consisting of transcription and translation where DNA instructions are converted into functional proteins that code for traits.

Ribosome

The cellular organelle located in the cytoplasm that functions as the protein factory where translation occurs.

Gene Mutation

An error made during DNA replication that produces a permanent sequence change in a single gene, occurring at a rare rate of approximately $1$ in $100{,}000{,}000$ bases.

Point Mutation

A gene mutation occurring at a single point in the DNA sequence that alters only one base pair through substitution, insertion, or deletion.

Frameshift Mutation

A mutation resulting from nucleotide insertions or deletions that alters the reading frame of triplets, changing every amino acid produced after the point of mutation.

Gene Expression

A regulated cellular process in which a specific gene is actively transcribed and translated to produce its protein product.

Cell Differentiation

The developmental process by which unspecialized cells (such as stem cells) develop specialized functions because specific genes are selectively turned on or off.

Introns

Non-coding segments of pre-mRNA transcribed from DNA that are excised and removed in the nucleus before mRNA enters the cytoplasm.

Exons

The expressed coding segments of mRNA that code for amino acids and are spliced together to form the mature mRNA molecule that exits the nucleus.

Start Codon

The mRNA codon AUG, which signals the start of translation and codes for the amino acid methionine.

Stop Codons

The three mRNA codons (UAG, UAA, and UGA) that do not code for amino acids and signal the ribosome to release the completed polypeptide.

Missense Mutation

A gene mutation error that alters a single codon so that it codes for a different amino acid, such as UGU (cysteine) changing to UGG (tryptophan).

Nonsense Mutation

A gene mutation error that converts a coding amino acid codon into a premature stop codon, such as UGU (cysteine) changing to UGA (stop), prematurely terminating the protein.

Silent Mutation

A gene mutation error that changes a nucleotide base but results in a codon that still codes for the exact same amino acid, leaving the protein unchanged.

Mutagenic Agent

An environmental physical or chemical agent, such as ultraviolet (UV) light or radiation, that directly causes genetic mutations in DNA.

Carcinogen

A cancer-causing agent capable of mutating DNA, including toxic chemicals (such as cigarette smoke components like benzene and arsenic) or viral agents (such as HPV).

Snorks

Hypothetical underwater organisms used to model protein synthesis and mutations, possessing four genes coding for 3-amino-acid traits including body color, head shape, number of eyes, and number of snorkels.