# Central dogma

Information in cells usually flows from DNA to RNA to protein. DNA is transcribed into RNA, and RNA is translated into protein.

Biology (university) · Part 04: DNA, transcription and translation · Card 4 of 9 · Last updated 2026-10-19

## Analogy

A recipe book (DNA), a photocopy of one recipe (RNA) and the finished dish (protein).

## In practice

Some viruses add a twist: retroviruses such as HIV copy RNA back into DNA.

## Practice

### Flashcards

- **State the central dogma.** DNA is transcribed to RNA, and RNA is translated into protein.

### Interview questions

**Explain how the information in a gene becomes a protein in a eukaryotic cell.**

- Transcription in nucleus makes pre-mRNA
- Splicing removes introns, cap and tail added
- mRNA exits to cytoplasm
- Ribosome reads codons with tRNA
- Amino acids joined and folded

## Questions people ask

### Is the central dogma always true?

It describes the usual flow, but there are exceptions. Retroviruses copy RNA into DNA using reverse transcriptase. Some RNAs, such as tRNA and rRNA, are never translated and work as RNA. The dogma says information does not flow back from protein to nucleic acid.

### What is the difference between genotype and phenotype?

Genotype is the set of alleles an organism carries, the DNA instructions. Phenotype is the visible or measurable result, such as eye colour or blood type. The central dogma links them: genes are expressed as proteins, which together with the environment produce the traits we see.

## Related concepts

- [Transcription](https://studyvisually.com/learn/science/biology-university/biology-university-part-4/biology-university-part-4-concept-5)
- [RNA splicing](https://studyvisually.com/learn/science/biology-university/biology-university-part-4/biology-university-part-4-concept-6)
- [Translation](https://studyvisually.com/learn/science/biology-university/biology-university-part-4/biology-university-part-4-concept-8)
- [Genetic code](https://studyvisually.com/learn/science/biology-university/biology-university-part-4/biology-university-part-4-concept-7)

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