D1.2 - Protein Synthesis
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38 Terms
Protein Synthesis
process by which cells produce proteins based on the genetic information encoded in DNA.”
Main stages
Transcription and translation.
Reliability of Protein Synthesis
complementary base pairing ensures accuracy.
Regulation of gene expression
To allow cells to differentiate and respond to environmental changes.
Transcription Initiation
RNA polymerase binding to the promoter region.
How does RNA polymerase synthesize mRNA?
By separating DNA strands and adding complementary RNA nucleotides.
What type of reaction forms mRNA?
Condensation reactions linking RNA nucleotides.
What base pairs occur between DNA and RNA?
A pairs with U, G pairs with C.
What stabilizes DNA–RNA base pairing?
Hydrogen bonds.
Where does translation occur?
In the ribosome.
. What is the role of mRNA in translation?
It carries the genetic code to the ribosome.
What is the role of tRNA?
It brings amino acids and matches anticodons to codons.
What is the role of ribosomes?
They catalyze peptide bond formation.
What are the three ribosomal tRNA sites?
A (aminoacyl), P (peptidyl), E (exit).
What triggers termination of translation?
A stop codon entering the ribosome.
What is a codon?
A three‑nucleotide sequence that specifies an amino acid.
How many codons exist?
64 possible codons.
What is degeneracy in the genetic code?
Multiple codons can code for the same amino acid.
What is the start codon and what does it code for?
AUG, coding for methionine.
What are the three stop codons?
UAA, UAG, UGA.
What does the codon CUA code for?
Leucine
Mutation
A change in the DNA sequence that may affect protein structure.
Point mutation
A mutation involving a single nucleotide change.
What are the three types of base substitution mutations
Silent, missense, and nonsense.
What mutation causes sickle cell anemia?
A base substitution in the hemoglobin gene replacing glutamic acid with valine.
What is a promoter?
A DNA sequence where RNA polymerase binds to start transcription.
What do transcription factors do?
They regulate gene expression by enhancing or inhibiting RNA polymerase binding.
What is non‑coding DNA?
DNA that does not code for proteins but regulates gene expression.
What are introns and exons?
Introns are removed non‑coding regions; exons remain and are translated.
What is added to the 5' end of mRNA?
A 5' cap.
What is added to the 3' end of mRNA?
A poly‑A tail.
What performs splicing?
Spliceosomes.
What is alternative splicing?
Producing different proteins by joining exons in various combinations.
What happens during initiation of translation?
The small ribosomal subunit binds mRNA at AUG, and tRNA enters the P site.
What happens during elongation?
Amino acids are added as the ribosome moves along mRNA.
What happens during termination?
A stop codon causes release of the polypeptide.
How is pre‑proinsulin processed?
Signal peptide removal forms proinsulin, then cleavage produces insulin.
What do proteasomes do?
They degrade damaged or unneeded proteins.