DNA Mutations, Gene Expression, Transcription, and Translation Flashcards
What are DNA mutations?
Changes in the nucleotide sequence of DNA.
What are the types of mutations?
Point mutations: Single nucleotide changes (e.g., substitution).
Insertions: Addition of one or more nucleotides.
Deletions: Loss of one or more nucleotides.
Frameshift mutations: Insertions or deletions altering the reading frame.
Silent mutations: No change in protein function.
Missense mutations: Change in one amino acid in the protein.
Nonsense mutations: Introduction of a premature stop codon.
What causes mutations?
Spontaneous mutations: Errors during DNA replication.
induced mutations: Caused by mutagens such as UV light, chemicals, or radiation.
What is gene expression?
The process by which information from a gene is used to synthesize functional gene products like proteins.
What are the levels of gene expression regulation?
Transcriptional: Control of mRNA synthesis.
Post-transcriptional: mRNA splicing, stability, and transport.
Translational: Regulation of protein synthesis.
Post-translational: Protein folding, modification, and degradation.
What is an operon?
A cluster of genes under the control of a single promoter, common in prokaryotes (e.g., lac operon).
What are enhancers and silencers?
Enhancers: DNA sequences that increase gene transcription.
Silencers: DNA sequences that repress gene transcription.
What role do transcription factors play?
Bind to promoter or enhancer regions to regulate gene expression.
What is transcription?
The synthesis of RNA from a DNA template.
What are the steps of transcription?
Initiation: RNA polymerase binds to the promoter region.
Elongation: RNA polymerase synthesizes RNA in the 5’ to 3’ direction.
Termination: RNA synthesis stops at the terminator sequence.
What are the differences between prokaryotic and eukaryotic transcription?
Prokaryotic: Occurs in the cytoplasm; mRNA is polycistronic.
Eukaryotic: Occurs in the nucleus; mRNA undergoes processing (capping, polyadenylation, splicing).
What is the role of RNA polymerase II?
Synthesizes mRNA in eukaryotes.
What is splicing?
Removal of introns from pre-mRNA and joining of exons.
What is translation?
The synthesis of proteins from an mRNA template.
What are the steps of translation?
Initiation: Ribosome assembles at the start codon (AUG).
Elongation: tRNA brings amino acids to the ribosome, and peptide bonds form.
Termination: Ribosome encounters a stop codon (UAA, UAG, UGA) and releases the polypeptide.
What is the role of tRNA?
Transfers specific amino acids to the ribosome.
Contains an anticodon that pairs with the mRNA codon.
What are ribosomes composed of?
rRNA and proteins, with small and large subunits.
What is the difference between prokaryotic and eukaryotic translation?
Prokaryotic: Coupled with transcription, occurs in the cytoplasm.
Eukaryotic: Separated from transcription, occurs in the cytoplasm after mRNA processing.
