Molecular Genetics: Transcription, Translation, Mutations, and Gene Transfer

Comprehensive practice flashcards defining key vocabulary related to DNA replication, transcription, translation, genetic mutations, repair mechanisms, and horizontal gene transfer in prokaryotes and eukaryotes.

DNA Polymerase

An enzyme responsible for synthesizing new DNA as well as proofreading and repairing base pairing errors during replication.

Semiconservative Replication

The replication process in which half of the original parental DNA molecule is conserved in each newly formed double-stranded DNA molecule.

Transcription

The process of using a template strand of DNA to synthesize a complementary strand of RNA.

RNA Polymerase

The enzyme that binds to DNA, reads the template strand bases, and synthesizes a complementary strand of RNA.

Promoter

A specific sequence of bases located at the beginning of a gene where RNA polymerase binds to initiate transcription.

Transcription Bubble

The localized unwound and unzipped region of DNA that moves along a gene during RNA synthesis and reseals as the enzyme passes.

Terminator

A specific sequence of bases at the end of a gene that signals RNA polymerase to detach from the DNA and release the completed RNA strand.

Introns

Portions of newly synthesized RNA in eukaryotic cells that are cut out and removed before the mature RNA molecule leaves the nucleus.

Translation

The second stage of protein synthesis in which the nucleotide sequence of messenger RNA is read to construct a specific chain of amino acids.

Codon

A group of three consecutive bases or nucleotides on DNA or messenger RNA that specifies a particular amino acid or stop signal.

Messenger RNA (mRNA)

The type of RNA synthesized during transcription that carries genetic directions from DNA to the ribosome for protein synthesis.

Ribosomal RNA (rRNA)

The RNA molecules that combine with proteins to form ribosomes, the structural sites of translation.

Transfer RNA (tRNA)

The type of RNA responsible for carrying specific amino acids to the ribosome to assemble a growing protein chain.

Anticodon

A sequence of three nucleotides at the bottom of a transfer RNA molecule that is complementary to a corresponding codon on messenger RNA.

Start Codon

The specific codon ($AUG$) at the beginning of messenger RNA that initiates translation and codes for the amino acid methionine.

Stop Codon

A messenger RNA sequence (such as $UAG$) that acts as a release factor to halt translation and release the completed protein chain.

Mutation

Any alteration or change in the base sequence of an organism's DNA.

Genotype

The actual genetic makeup or collection of genes in an organism.

Phenotype

The observable physical characteristics or appearance of an organism.

Point Mutation

A mutation that involves a single base substitution in the DNA sequence.

Missense Point Mutation

A base substitution that alters a codon so that it codes for a different amino acid, changing the meaning of the resulting protein.

Nonsense Point Mutation

A base substitution that changes an amino acid codon into a premature stop codon, leading to an abnormally truncated protein.

Silent Point Mutation

A base substitution that alters a nucleotide but still codes for the same amino acid, producing a genotypic change without altering the phenotype.

Frameshift Mutation

A mutation caused by the insertion or deletion of a base, which alters the three-base reading frame of codons downstream of the mutation site.

Spontaneous Mutation

A naturally occurring genetic change caused by an uncorrected error during DNA replication by DNA polymerase.

Induced Mutation

A mutation caused by an external agent that raises the mutation rate above baseline levels.

Mutagen

A chemical or physical agent, such as radiation, that alters DNA and increases the rate of mutation.

Mutation Rate

The baseline frequency at which mutations occur per cell division.

Thymine Dimer

An abnormal bond formed between adjacent thymine bases on the same DNA strand as a result of exposure to ultraviolet radiation.

Nucleotide Excision Repair

A DNA repair mechanism where enzymes cut out a damaged section of DNA and DNA polymerase synthesizes replacement DNA.

Photoreactivation (Light Repair)

A repair process in which a light-dependent enzyme directly breaks the bonds between adjacent thymines in a thymine dimer.

Photolyase

An enzyme required for photoreactivation that breaks the covalent bond between thymines in a thymine dimer when activated by visible light.

Vertical Gene Transfer

The transmission of genetic information from parent organisms to their offspring, such as through binary fission or sexual reproduction.

Horizontal Gene Transfer

The passage of genetic material between individual organisms belonging to the same generation.

Conjugation

A type of horizontal gene transfer in bacteria where genetic material is passed directly between two cells connected by a hollow pilus.

Conjugation Pilus

A hollow tubular appendage produced by a bacterium that allows it to transfer genetic information directly into another cell.

Transduction

A mechanism of horizontal gene transfer in which a bacteriophage virus accidentally packages bacterial DNA and transfers it to another bacterium.

Bacteriophage

A virus that infects bacteria and can serve as a vector for transferring bacterial genetic material.

Transformation

A mechanism of horizontal gene transfer in which a bacterial cell takes up free DNA from its surrounding environment and incorporates it into its genome.