Protein Synthesis, Gene Expression & Mutations

Vocabulary flashcards summarizing the essential terms related to protein synthesis, gene expression, and DNA mutations.

DNA

Double-stranded nucleic acid that stores hereditary information inside the nucleus and forms chromosomes.

Chromosome

Tightly packed DNA molecule containing many genes.

Gene

A specific DNA sequence that encodes one protein.

Genome

All the genetic information of an organism.

Transcription

Process of copying DNA into RNA by RNA polymerase.

RNA Processing

Modifications that convert pre-mRNA into mature mRNA (capping, tailing, splicing).

Translation

Decoding mRNA into an amino-acid chain (polypeptide) at ribosomes in the cytoplasm.

Central Dogma

Flow of genetic information: DNA → RNA → Protein.

DNA vs. RNA – Sugar

DNA contains deoxyribose; RNA contains ribose.

DNA vs. RNA – Bases

DNA uses A, G, C, T; RNA uses A, G, C, U.

DNA vs. RNA – Strands

DNA is double-stranded; RNA is usually single-stranded.

mRNA (Messenger RNA)

RNA copy of a gene that carries coding information from nucleus to ribosome.

rRNA (Ribosomal RNA)

RNA that combines with proteins to form ribosomes and helps decode mRNA.

tRNA (Transfer RNA)

Adapter molecule that delivers specific amino acids to the ribosome via its anticodon.

Promoter

DNA region upstream of a gene where transcription factors and RNA polymerase bind.

Transcription Factor

Protein that regulates transcription by binding DNA and assisting RNA polymerase.

RNA Polymerase

Enzyme that synthesizes RNA from a DNA template.

Transcription Initiation

Stage where transcription factors, RNA polymerase, and promoter assemble; DNA unwinds.

Transcription Elongation

RNA polymerase adds complementary RNA nucleotides 5′→3′.

Transcription Termination

RNA polymerase stops at termination sequence and releases RNA transcript.

Pre-mRNA

Initial RNA transcript containing both introns and exons.

5′ Cap

Modified guanine added to 5′ end of mRNA to aid ribosome binding.

Poly-A Tail

String of ~150 adenines on 3′ end that protects mRNA from degradation.

Intron

Non-coding RNA segment removed during splicing.

Exon

Coding RNA segment retained in mature mRNA.

Spliceosome

Enzyme complex that excises introns and joins exons.

Codon

Sequence of three mRNA nucleotides that specifies an amino acid.

Anticodon

Three-base sequence on tRNA complementary to an mRNA codon.

Genetic Code

Set of 64 codons translating nucleotide language into 20 amino acids; redundant and universal.

Start Codon

AUG; signals initiation and codes for methionine.

Stop Codon

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

Reading Frame

Grouping of mRNA bases into consecutive codons; set by AUG.

Ribosome

Cellular machine (rRNA + proteins) that coordinates translation.

A Site

Ribosome site where incoming amino-acyl tRNA binds.

P Site

Ribosome site holding tRNA with growing polypeptide.

E Site

Exit site where spent tRNA leaves the ribosome.

Polypeptide

Chain of amino acids produced during translation.

Peptide Bond

Covalent bond linking amino acids in a protein.

Polyribosome

Multiple ribosomes translating the same mRNA simultaneously.

Protein Folding

Process by which a polypeptide acquires its functional three-dimensional shape.

Point Mutation

Single nucleotide substitution in DNA.

Silent Mutation

Point mutation yielding same amino acid; no change in protein function.

Missense Mutation

Point mutation changing one amino acid in the protein.

Conservative Missense

Amino-acid change to a chemically similar residue; minor effect.

Non-conservative Missense

Amino-acid change to a chemically different residue; major effect (e.g., sickle-cell).

Nonsense Mutation

Point mutation that converts a codon into a premature stop codon.

Frameshift Mutation

Insertion or deletion that shifts the reading frame of mRNA.

Fragile X Syndrome

Disorder from CGG repeat insertions on X-chromosome causing mental impairment.

Cystic Fibrosis

Autosomal recessive disease from frameshift mutations in chloride channel gene.

Thymine Dimer

UV-induced covalent link between adjacent thymine bases causing DNA distortion.

Mutagen

Agent that increases mutation rate (e.g., UV, chemicals).

Ames Test

Assay using histidine-dependent bacteria to detect chemical mutagens by reversion growth.

Somatic Mutation

DNA change in non-gamete cells; not inherited but can cause cancer.

Germ-line Mutation

Mutation in eggs or sperm; heritable and may cause birth defects.

Teratology

Study of abnormal embryonic development and birth defects.