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IB Biology SL A1.2 Nucleic Acids Questions

Practise IB Biology SL A1.2 with questions on nucleotide structure, DNA and RNA, complementary base pairing and genetic information.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • Identify phosphate, pentose and nitrogenous-base components; show the covalent phosphate–sugar backbone and use nucleotide counts to infer phosphate totals.
  • Compare DNA and RNA using pentose sugar, thymine or uracil, strand organisation and typical length, and identify a molecule from a sequence or diagram.
  • Draw or interpret a DNA double helix with antiparallel sugar–phosphate strands, complementary A–T/G–C pairs and hydrogen bonds; distinguish these from covalent backbone links and use base-pair data to calculate missing percentages.
  • Relate the order of DNA bases and genome size to stored information, and use universal-code evidence to explain gene transfer and conserved protein sequences.
  • Use transformation, genome-source and cloning evidence to identify DNA as genetic material and distinguish nuclear from mitochondrial inheritance.

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 code

Question 1

[Maximum number: 1]

The image shows the results of Griffith's experiment with S and R strains of Streptococcus pneumoniae in mice (Mus musculus).

Figure for Question 1 — IB Biology SL

What is an explanation for the results?

A

Mice vary in their resistance to bacteria.

B

The R strain and S strain mated.

C

R strain bacteria are more heat-stable than S strain.

D

DNA was transferred from heat-killed S cells to R cells.

Question 2

[Maximum number: 6]

Question (a)

(a)

The diagram below represents a DNA nucleotide.

Figure for Question (a) — IB Biology SL

Identify the phosphate group and deoxyribose.

Phosphate group:
Deoxyribose:

[ 1 ]

Question (b)

(b)

Draw a labelled diagram to show how four nucleotides are joined together to form a double-stranded DNA molecule with two base pairs.

Figure for Question (b) — IB Biology SL
[ 3 ]

Question (c)

(c)

State two differences between RNA and DNA nucleotides.

[ 2 ]

Question 3

[Maximum number: 2]

Outline the bonding between DNA nucleotides.

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