Quiz 2 a Central Dogma -
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What is the central dogma of molecular biology?
The flow of genetic information: DNA → RNA → Protein.
Which enzyme synthesises RNA from a DNA template during transcription?
RNA polymerase.
What is the start codon for translation in most organisms?
AUG — it codes for the amino acid methionine.
Which RNA carries amino acids to the ribosome?
tRNA — transfer RNA acts as an adaptor between codons and amino acids.
Which of the following is a stop codon in translation?
UAA (others are UAG and UGA).
Which DNA strand serves as the template for transcription?
The template (antisense) strand — complementary to the coding (sense) strand.
What is the role of promoter sequences in transcription?
They provide a binding site for RNA polymerase and transcription factors, determining where transcription begins and controlling gene expression.
What is the function of the terminator region in transcription?
It signals RNA polymerase to stop transcription and release the newly formed RNA transcript.
List the main steps of translation.
Initiation, Elongation, and Termination.
What type of bond forms between amino acids during translation?
A peptide bond, catalysed by rRNA’s ribozyme activity in the ribosome.
What amino acid does the initiator tRNA carry in eukaryotes?
Methionine, encoded by the start codon AUG.
What is the function of mRNA in translation?
mRNA carries the genetic code from DNA to the ribosome; each codon corresponds to an amino acid or stop signal.
What is the function of tRNA in translation?
tRNA delivers specific amino acids to the ribosome; its anticodon pairs with the complementary mRNA codon.
What is the function of rRNA in translation?
rRNA forms the structural and catalytic core of ribosomes and catalyses peptide bond formation.
Why are promoters and terminators important in transcription?
They ensure RNA polymerase starts and stops at the correct locations, producing accurate RNA molecules.
How can a mutation in the promoter region affect transcription?
It may reduce or prevent RNA polymerase binding, decreasing or stopping transcription of that gene.
How can mutations in coding sequences affect translation?
They can alter the mRNA codons, causing missense, nonsense, or frameshift mutations that change the protein’s amino acid sequence and function.
What is a missense mutation?
A single-base change that substitutes one amino acid for another in the protein.
What is a nonsense mutation?
A base substitution that introduces a premature stop codon, truncating the protein.
What is a frameshift mutation?
An insertion or deletion that shifts the reading frame, altering all downstream amino acids.
What is a silent mutation?
A DNA change that does not alter the amino acid sequence due to redundancy in the genetic code.
How can mutations affect an organism?
Effects range from harmless to severe; they can cause dysfunctional proteins (e.g., sickle-cell anaemia) or provide beneficial variation for evolution.
How does RNA polymerase know where to start transcription?
It recognises and binds to promoter sequences with the help of transcription factors.
What happens if transcription lacks a terminator sequence?
RNA polymerase would continue transcribing downstream DNA, producing an overly long or faulty mRNA.