DNA Quiz

Twenty parts to find across five DNA drawings, from the base pairs to the ribosome.

DNA Quiz

Name Date

Tap the nucleotide

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Write the name of each numbered part.Answer key

  1. Sugar-phosphate backbone
  2. Base pair
  3. Major groove
  4. Minor groove
  5. Phosphate group
  6. Deoxyribose (sugar)
  7. Adenine (A)
  8. Thymine (T)
  9. Guanine (G)
  10. Cytosine (C)
  11. Hydrogen bonds
  12. Nucleotide
  13. Five prime end
  14. Three prime end
  15. Phosphate group
  16. Pentose sugar
  17. Nitrogenous base
  18. 1′ carbon
  19. 2′ carbon
  20. 3′ carbon
  21. 4′ carbon
  22. 5′ carbon
  23. 3′ hydroxyl group
  24. Glycosidic bond
  25. Purine
  26. Pyrimidine
  27. Replication fork
  28. Template strand (parent strand)
  29. Leading strand
  30. Lagging strand
  31. Okazaki fragment
  32. RNA primer
  33. Helicase
  34. Topoisomerase
  35. Single-strand binding proteins
  36. Primase
  37. DNA polymerase III
  38. Sliding clamp
  39. DNA polymerase I
  40. DNA ligase
  41. DNA
  42. RNA polymerase
  43. Transcription
  44. mRNA
  45. Nucleus
  46. Nuclear pore
  47. Cytoplasm
  48. Translation
  49. Ribosome
  50. tRNA
  51. Amino acid
  52. Polypeptide chain
  53. Protein
  54. mRNA (messenger RNA)
  55. Start codon (AUG)
  56. Stop codon
  57. Codon
  58. Small ribosomal subunit
  59. Large ribosomal subunit
  60. E site (exit site)
  61. P site (peptidyl site)
  62. A site (aminoacyl site)
  63. tRNA (transfer RNA)
  64. Anticodon
  65. Amino acid
  66. Polypeptide chain
  67. Peptide bond

Double helix: Drawn for this site by script, 2026-09-26. Licence: own work. Nucleotide: Drawn for this site by script, 2026-09-27. Licence: own work. Replication: Drawn for this site by script, 2026-09-26. Licence: own work. Protein synthesis: Drawn for this site by script, 2026-09-27. Licence: own work. Translation: Drawn for this site by script, 2026-09-26. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: the double helix at full size

All 67 parts on the diagram

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Double helix 14

  1. Sugar-phosphate backbone Alternating sugars and phosphates; the bases hang inward from it.
  2. Base pair Two bases on opposite strands held together by hydrogen bonds.
  3. Major groove The wide gap between the strands; proteins bind DNA there.
  4. Minor groove The narrow gap between the strands, alternating with the major groove.
  5. Phosphate group Links one sugar to the next; it makes DNA acidic.
  6. Deoxyribose (sugar) The five-carbon sugar of DNA; RNA has ribose instead.
  7. Adenine (A) A purine; it pairs with thymine by two hydrogen bonds.
  8. Thymine (T) A pyrimidine; it pairs with adenine.
  9. Guanine (G) A purine; it pairs with cytosine by three hydrogen bonds.
  10. Cytosine (C) A pyrimidine; it pairs with guanine.
  11. Hydrogen bonds Weak bonds holding the pairs: two for A-T, three for G-C.
  12. Nucleotide One unit of DNA: a phosphate, a sugar and a base.
  13. Five prime end The strand end with a free phosphate on the sugar's 5' carbon.
  14. Three prime end The strand end with a free hydroxyl on the sugar's 3' carbon.

Nucleotide 12

  1. Phosphate group A phosphorus atom with four oxygens round it. It is joined to the sugar's 5′ carbon. In a strand it also joins the 3′ carbon of the next sugar.
  2. Pentose sugar A five-carbon sugar: deoxyribose in DNA, ribose in RNA. Four of its carbons and one oxygen make the ring.
  3. Nitrogenous base The part that carries the genetic code. It is adenine, guanine, cytosine or thymine in DNA, with uracil in place of thymine in RNA. This one is a purine.
  4. 1′ carbon The sugar's first carbon, where the base is joined.
  5. 2′ carbon In DNA it carries only a hydrogen. In RNA it carries a hydroxyl group. That missing oxygen is the deoxy in deoxyribose.
  6. 3′ carbon The carbon that carries the 3′ hydroxyl. The next nucleotide joins there in a strand.
  7. 4′ carbon The last carbon in the ring, next to the ring oxygen. It holds the 5′ carbon outside the ring.
  8. 5′ carbon The one carbon outside the ring, joined to the phosphate group.
  9. 3′ hydroxyl group An oxygen and a hydrogen on the 3′ carbon. The next nucleotide's phosphate joins here, so a strand grows at its 3′ end.
  10. Glycosidic bond The bond that joins the base to the sugar's 1′ carbon.
  11. Purine A base with two rings. A six-sided ring is joined to a five-sided one. Adenine and guanine are purines.
  12. Pyrimidine A base with one six-sided ring. Cytosine, thymine and uracil are pyrimidines.

Replication 14

  1. Replication fork Where the parent helix opens into two template strands.
  2. Template strand (parent strand) An old strand that each new strand is copied from.
  3. Leading strand Made continuously, towards the fork.
  4. Lagging strand Made in short pieces, away from the fork.
  5. Okazaki fragment A short stretch of the lagging strand, later joined up.
  6. RNA primer A short RNA start that DNA polymerase extends.
  7. Helicase Unzips the helix by breaking the hydrogen bonds.
  8. Topoisomerase Relieves over-winding ahead of the fork with temporary nicks.
  9. Single-strand binding proteins Coat the single strands so they do not rejoin.
  10. Primase Makes each RNA primer.
  11. DNA polymerase III The main enzyme adding nucleotides, 5' to 3'.
  12. Sliding clamp Holds DNA polymerase on the strand.
  13. DNA polymerase I Removes RNA primers and fills in DNA.
  14. DNA ligase Seals the gap between fragments.

Protein synthesis 13

  1. DNA The cell's genetic code, kept in the nucleus. The stretch of it that codes for one protein is a gene.
  2. RNA polymerase The enzyme that opens the DNA and reads the gene. It builds a matching strand of mRNA.
  3. Transcription The first stage, in the nucleus. A gene in the DNA is copied into mRNA.
  4. mRNA Messenger RNA, the copy of the gene. It carries the code out of the nucleus to a ribosome.
  5. Nucleus The part of the cell that holds the DNA. Transcription happens here.
  6. Nuclear pore A gap in the envelope round the nucleus. The finished mRNA leaves the nucleus through one.
  7. Cytoplasm The inside of the cell outside the nucleus. Translation happens here.
  8. Translation The second stage, at a ribosome in the cytoplasm. The mRNA's code is read and amino acids are joined in that order.
  9. Ribosome Reads the mRNA one codon (three bases) at a time. It joins the amino acids. It has a large and a small subunit.
  10. tRNA Transfer RNA brings one amino acid. Its anticodon pairs with the matching codon on the mRNA.
  11. Amino acid One building block of a protein. Carried on the end of a tRNA.
  12. Polypeptide chain The chain of amino acids the ribosome builds, one at a time.
  13. Protein The finished molecule: the polypeptide chain folded into its working shape.

Translation 14

  1. mRNA (messenger RNA) Carries the gene's code from the DNA; the ribosome reads it three bases at a time, from 5' to 3'.
  2. Start codon (AUG) AUG, the codon where translation starts; it codes for methionine.
  3. Stop codon UAA, UAG or UGA: no tRNA matches it, so a release factor ends translation there.
  4. Codon Three mRNA bases that code for one amino acid; this one sits in the A site.
  5. Small ribosomal subunit The smaller part of the ribosome; it binds the mRNA.
  6. Large ribosomal subunit The larger part of the ribosome; it holds the three tRNA sites and joins the amino acids.
  7. E site (exit site) Where the empty tRNA leaves the ribosome.
  8. P site (peptidyl site) Holds the tRNA carrying the growing chain.
  9. A site (aminoacyl site) Where each new tRNA with its amino acid comes in.
  10. tRNA (transfer RNA) Brings one amino acid and matches it to a codon with its anticodon.
  11. Anticodon Three tRNA bases that pair with the matching codon on the mRNA.
  12. Amino acid One building block of a protein, carried in by its tRNA.
  13. Polypeptide chain The growing chain of amino acids that will fold into a protein.
  14. Peptide bond The bond joining one amino acid to the next.

Double helix, the list: Read 2026-09-26. OpenStax Biology 2e, 14.2 DNA Structure and Sequencing, https://openstax.org/books/biology-2e/pages/14-2-dna-structure-and-sequencing : a nucleotide is a nitrogenous base, a five-carbon sugar and a phosphate group; the sugar is deoxyribose in DNA and ribose in RNA; purines adenine and guanine, pyrimidines cytosine and thymine (pyrimidines smaller, a single six-membered ring); A pa Licence: own work The drawing: Drawn for this site by script, 2026-09-26. Own work. Licence: own work

Nucleotide, the list: Read 2026-09-27. (1) Wikipedia, Nucleotide, https://en.wikipedia.org/wiki/Nucleotide : three parts, a nitrogenous base (nucleobase), a five-carbon sugar (ribose or deoxyribose) and a phosphate group; adenine and guanine are purines, cytosine, thymine and uracil pyrimidines; thymine in DNA, uracil in RNA; the glycosidic bond joins base and sugar. (2) Wikipedia, Deoxyribose, https://en.wikipedia.org Licence: own work The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work

Replication, the list: Read 2026-09-26. OpenStax Biology 2e, 14.4 DNA Replication in Prokaryotes, https://openstax.org/books/biology-2e/pages/14-4-dna-replication-in-prokaryotes : helicase separates the strands at the replication fork; single-strand binding proteins stop them rewinding; topoisomerase prevents over-winding ahead of the fork with temporary nicks; primase makes an RNA primer; DNA polymerase III adds nucleo Licence: own work The drawing: Drawn for this site by script, 2026-09-26. Licence: own work

Protein synthesis, the list: Read 2026-09-27. (1) Wikipedia, Protein biosynthesis, https://en.wikipedia.org/wiki/Protein_biosynthesis : two stages; in transcription, in the nucleus, RNA polymerases convert a gene into mRNA; the mature mRNA leaves the nucleus through nuclear pores to the cytoplasm; in translation, ribosomes read the mRNA and join amino acids brought by tRNA, whose anticodon pairs with each codon; the polypepti Licence: own work The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work

Translation, the list: Read 2026-09-26. OpenStax Biology 2e, 15.5 Ribosomes and Protein Synthesis, https://openstax.org/books/biology-2e/pages/15-5-ribosomes-and-protein-synthesis : small and large ribosomal subunits; mRNA read 5' to 3'; the AUG start codon; charged tRNAs enter the A site and the anticodon base-pairs with the codon; after peptide bond formation the A-site tRNA moves to the P site and the empty P-site tR Licence: own work The drawing: Drawn for this site by script, 2026-09-26. Own work, nothing traced. Licence: own work

How it works

A DNA unit test covers more than the double helix. This quiz mixes five drawings, the helix, a nucleotide, replication, protein synthesis and translation, and asks you to find 20 parts across them.

Read the full guide

One round, five drawings

Each question shows the drawing its part is on and names the part; tap it. The chips above the drawing make a round about one drawing only, such as replication. After the round, the drawing you missed most is the one to study next. Each drawing also has a page of its own, with every part in study mode, for revising before you try the round again.

  • A is always paired with T and C with G, which is why the two strands carry the same code.

Questions and answers

What does a DNA quiz usually cover?

The structure of DNA (the double helix, nucleotides, base pairs and the sugar-phosphate backbone), how DNA copies itself in replication, and how its code is read to make proteins in transcription and translation.

What are the parts of a DNA nucleotide?

A phosphate group, a sugar called deoxyribose, and one of four nitrogenous bases: adenine, thymine, cytosine or guanine.

Which bases pair together in DNA?

Adenine pairs with thymine, and cytosine pairs with guanine. The pairs are held together by hydrogen bonds between the two strands.

What happens in DNA replication?

The two strands unzip at the replication fork, and each old strand is used as a template for a new partner strand. Each new DNA molecule keeps one old strand and one new one.

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