9700 · 6.2
Protein synthesis flashcards
Revision flashcards for Cambridge 9700 Protein synthesis (syllabus 6.2). Flip, recall, then mark a real past-paper question.
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What is transcription?
The process in the nucleus (eukaryotes) where a gene's DNA sequence is copied by RNA polymerase to create a complementary messenger RNA (mRNA) molecule.
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What is translation?
The process in the cytoplasm on ribosomes where the genetic code on an mRNA molecule is decoded to synthesise a specific polypeptide chain (protein).
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Define 'codon'.
A sequence of three consecutive nucleotide bases on an mRNA molecule that specifies a single amino acid or a stop signal during protein synthesis.
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What is the role of tRNA?
Transfer RNA (tRNA) acts as an adaptor molecule. It carries a specific amino acid to the ribosome and has an anticodon that pairs with the complementary codon on the mRNA.
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What does it mean for the genetic code to be 'degenerate'?
It means that most amino acids are coded for by more than one mRNA codon. This provides some protection against the effects of point mutations.
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What is an intron?
A non-coding segment of a gene in eukaryotes that is transcribed into pre-mRNA but is removed by splicing before the mRNA is translated.
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What is an exon?
A coding segment of a gene in eukaryotes that is transcribed and retained in the mature mRNA after splicing. Exons are expressed to form the final polypeptide.
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What are the three sites on a ribosome for tRNA binding?
The A (aminoacyl) site, where a new tRNA arrives; the P (peptidyl) site, which holds the tRNA with the growing polypeptide chain; and the E (exit) site, where the empty tRNA leaves.