Chemistry Labs

Biochemistry and biomedical chemistry

Replication, transcription, translation

Cells copy genetic material, transcribe selected DNA segments into RNA, and translate messenger RNA into polypeptides.

1 Lower secondary2 Upper secondary3 Undergraduate4 Advanced5 Research

IntuitionIntuition: the central idea

Cells copy genetic material, transcribe selected DNA segments into RNA, and translate messenger RNA into polypeptides.

Explore the schematic model; it illustrates a concept rather than replacing experimental evidence.

SchoolSchool level: key concepts and a first application

Definition: Core concept

DNA polymerases extend a primer 5′→3′ using a template; RNA polymerase synthesizes RNA from DNA; ribosomes decode mRNA codons with tRNAs.

Replication uses DNA polymerases and proofreading; transcription uses RNA polymerase and promoter recognition; translation uses ribosomes, tRNAs and a nearly universal genetic code.

Key terms and meaning
TermInterpretation
ReplicationCopying of double-stranded DNA before cell division.
TranscriptionRNA synthesis using one DNA strand as template.
TranslationRibosomal decoding of mRNA into a polypeptide.

Example: Apply the idea

A coding DNA strand contains 5′-ATG GAA TAA-3′. Write the corresponding mRNA sequence.

Solution

The mRNA is 5′-AUG GAA UAA-3′: it matches the coding strand with U replacing T. Translation begins at AUG and UAA is a stop codon.

UndergraduateUniversity level: quantitative description

DNA→transcriptionRNA→translationpolypeptide\text{DNA}\xrightarrow{\text{transcription}}\text{RNA}\xrightarrow{\text{translation}}\text{polypeptide}

The universal genetic code maps 61 sense codons to 20 amino acids and uses three stop codons. wobble pairing makes the code degenerate at the third codon position.

References