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IB Biology HL A1.2 Nucleic Acids Questions

Practise IB Biology HL A1.2 with questions on nucleotide structure, DNA and RNA, complementary pairing and the information stored in sequences.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Draw and label DNA or RNA nucleotides, then show how covalent sugar-phosphate bonds form a polynucleotide.
  • Compare DNA and RNA using their sugars, bases, strand structure and complementary pairing.
  • Explain antiparallel DNA double-helix structure using purine–pyrimidine pairing, hydrogen bonds and 5′/3′ directionality.
  • Use complementary sequences and genetic-code evidence to infer base-sequence diversity, conserved information and DNA/RNA relationships.
  • Interpret X-ray diffraction and Hershey–Chase evidence to justify DNA as genetic material and support the double-helix model.
  • Describe nucleosomes as DNA wrapped around histone octamers and explain their roles in chromosome packing and transcription regulation.

Covered syllabus points

A1.2.1—DNA as genetic materialA1.2.2—Components of a nucleotideA1.2.3—Sugar-phosphate bondingA1.2.4—Bases form the basis of a codeA1.2.5—RNA as a polymerA1.2.6—DNA as a double helixA1.2.7—Differences between DNA and RNAA1.2.8—Complementary base pairingA1.2.9—Diversity of DNA base sequencesA1.2.10—Conservation of genetic codeA1.2.11 (HL)—Directionality of RNA and DNAA1.2.12 (HL)—Purine-to-pyrimidine bonding and helix stabilityA1.2.13 (HL)—Structure of a nucleosomeA1.2.14 (HL)—Hershey-Chase experimentA1.2.15 (HL)—Chargaff's data

Question 1

[Maximum number: 3]

Draw a labelled diagram to show the structure of a single nucleotide of RNA.

Question 2

[Maximum number: 1]

What is the arrangement of the components of nucleotides in a single DNA strand?

A
Figure for Question 2 — IB Biology HL — Option A
B
Figure for Question 2 — IB Biology HL — Option B
C
Figure for Question 2 — IB Biology HL — Option C
D
Figure for Question 2 — IB Biology HL — Option D

Question 3

[Maximum number: 5]

Draw a labelled diagram of the molecular structure of DNA, comprising of four nucleotides.

Question 4

[Maximum number: 1]

The diagram shows a nucleic acid, with some of the bases indicated.

Figure for Question 4 — IB Biology HL

Identify the type of nucleic acid shown in the diagram.

Question 5

[Maximum number: 1]

The diagram shows a nucleic acid, with some of the bases indicated.

Figure for Question 5 — IB Biology HL

Deduce the base indicated by X on the diagram.

Question 6

[Maximum number: 4]

At all levels of biological organization there is diversity.

Explain the diversity of possible base sequences in nucleic acids.

Question 7

[Maximum number: 1]

What provides evidence for the universal nature of the genetic code?

A

Uracil replaces thymine in RNA

B

The amount of A is equal to the amount of T and the amount of G is equal to the amount of C

C

Nucleic acids contain the same bases in all species

D

mRNA codons are assigned to the same amino acids in different species

Question 8

[Maximum number: 1]

The diagram shows a nucleic acid, with some of the bases indicated.

Figure for Question 8 — IB Biology HL

Identify the terminal indicated by Y on the diagram.

Question 9

[Maximum number: 1]

Nucleosomes help to regulate transcription in eukaryotes.

State the components of a nucleosome.

Question 10

[Maximum number: 3]

The Hershey and Chase experiment supported DNA as the hereditary material.

Describe the experiment.

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