Lecture 8 Notes: DNA to Protein — Transcription, Translation, and Mutations (Vocabulary)

Vocabulary flashcards covering key concepts from the lecture on transcription, translation, mRNA processing, ribosomes, tRNA, codons, genetic code, and mutations.

DNA

Deoxyribonucleic acid that stores genetic information used to produce RNA and ultimately proteins; located in the nucleus and serves as the template for transcription.

RNA

Ribonucleic acid used to transfer the genetic information from DNA to the protein-synthesis machinery; includes mRNA, tRNA, and rRNA.

Gene

A region of DNA that can be expressed to produce a functional product (polypeptide or RNA).

Central dogma

Flow of genetic information: DNA -> RNA -> Protein.

Transcription

Synthesis of RNA under the direction of DNA; DNA is rewritten as RNA.

Translation

Synthesis of a polypeptide under the direction of RNA; RNA guides the assembly of amino acids into a protein.

mRNA (messenger RNA)

RNA that conveys genetic messages from DNA to the ribosome; in eukaryotes must exit the nucleus to the cytoplasm.

Introns

Intervening sequences in eukaryotic genes that are removed during RNA processing.

Exons

Coding regions that are joined to form mature mRNA and exit the nucleus.

RNA splicing

Process of removing introns and joining exons to produce a continuous coding sequence.

5' cap

Guanine-rich cap added to the 5' end of mRNA to aid export, stability, and ribosome binding.

Poly-A tail

Polyadenine tail added to the 3' end of mRNA; protects from degradation and aids export.

mRNA processing

Modifications including splicing, 5' cap addition, and 3' poly-A tail addition before mRNA leaves the nucleus.

Codon

A three-nucleotide unit in mRNA that specifies a particular amino acid or a stop signal.

Triplet code

Genetic code where three nucleotides encode one amino acid.

Start codon

AUG; codes for methionine and initiates translation.

Stop codon

UAA, UAG, or UGA; signals termination of translation.

Anticodon

A three-nucleotide sequence in tRNA that pairs with a complementary codon in mRNA.

tRNA (transfer RNA)

RNA molecules that deliver specific amino acids to the growing polypeptide during translation.

Amino acid

Building blocks of proteins that are added to a growing polypeptide chain during translation.

Ribosome

Molecular machine that coordinates mRNA and tRNA during protein synthesis; consists of small and large subunits.

A site

Ribosome site where incoming charged tRNA brings the next amino acid.

P site

Ribosome site where the growing polypeptide is attached to tRNA.

Genetic code

Set of rules that defines how codons map to amino acids; includes codon-to-amino-acid mappings.

Redundant (degenerate) code

More than one codon can encode the same amino acid.

Unambiguous code

Each codon specifies a single amino acid (or stop signal).

Nearly universal code

The genetic code is shared by most organisms from bacteria to plants and animals.

Nonoverlapping code

Codons are read in sequence with no overlap between them.

64 codons

Total number of codons possible from four RNA bases taken three at a time.

61 codons

Codons that specify amino acids (the remaining codons are stop signals).

Mutation

Any change in the nucleotide sequence of DNA.

Base substitution

Replacement of one nucleotide by another in DNA.

Silent mutation

A base substitution that does not change the amino acid sequence.

Missense mutation

A base substitution that changes one amino acid in the protein.

Nonsense mutation

A base substitution that creates a premature stop codon.

Deletion

Loss of one or more nucleotides, which can shift the reading frame.

Insertion

Addition of one or more nucleotides, which can shift the reading frame.

Frameshift mutation

Mutations that shift the reading frame, altering downstream amino acids.

Mutagen

Agent that increases the rate of mutation (e.g., radiation, chemicals).

Spontaneous mutation

Mutations that arise naturally during DNA replication or recombination without external influence.

DNA repair

Cellular processes that correct DNA damage and errors to maintain genome integrity.

Proofreading

DNA polymerase activity that checks and corrects errors during replication.

Mismatch repair

System that fixes mispaired bases after DNA replication.

Excision repair

Repair pathway that removes and replaces damaged DNA segments.

Reactive oxygen species

Reactive molecules produced by normal metabolism that can damage DNA.