A gene is a base sequence of DNA that codes for: the amino acid sequence of a polypeptide; or a functional RNA (including rRNA and tRNAs)
A gene is a specific sequence of DNA bases. It either carries instructions for building a protein, or it produces an RNA molecule that the cell uses directly.
Real World
The beta-globin gene on chromosome 11 specifies the exact 146-amino-acid sequence of haemoglobin's beta chain; a single base change in this gene causes the misfolded protein responsible for sickle-cell anaemia.
Exam Focus
Always include both options in a definition — a gene codes for a polypeptide OR a functional RNA such as tRNA or rRNA.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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