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Unit 4: Heredity and continuity of life
Quick questions on Transcription, translation and the genetic code (QCE Biology Unit 4)
12short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is transcription?Show answer
Location. Nucleus in eukaryotes, cytoplasm in prokaryotes.
What is the genetic code?Show answer
The genetic code links sequences of nucleotides in mRNA to sequences of amino acids in protein. Its key features:
What is translation?Show answer
Location. Cytoplasm, on ribosomes (free or membrane-bound).
What is prokaryotic versus eukaryotic expression?Show answer
The lac operon in E. coli is the classic prokaryotic example: three genes for lactose metabolism transcribed from one promoter, with a repressor that releases when lactose is present.
What is location?Show answer
Nucleus in eukaryotes, cytoplasm in prokaryotes.
What is enzyme?Show answer
RNA polymerase. It binds to a region of DNA called the promoter just upstream of the gene, unwinds a short stretch of the double helix and reads the template strand in the 3 prime to 5 prime direction.
What is eukaryotic processing?Show answer
The primary transcript (pre-mRNA) is modified before leaving the nucleus.
What is using the template strand directly as the protein code?Show answer
The mRNA is complementary to the template strand. The mRNA reads the same as the non-template strand except U replaces T.
What is forgetting the start codon codes for an amino acid?Show answer
AUG codes for methionine in addition to being the start signal.
What is saying stop codons code for an amino acid?Show answer
Stop codons do not code for any amino acid; they signal termination.
What is saying tRNAs read DNA?Show answer
tRNAs read mRNA codons through their anticodons.
What is treating introns as junk?Show answer
Introns can contain regulatory sequences and enable alternative splicing.