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
The image shows the results of Griffith's experiment with S and R strains of Streptococcus pneumoniae in mice (Mus musculus).
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
Question (a)
(a)
The diagram below represents a DNA nucleotide.
Identify the phosphate group and deoxyribose.
Phosphate group:
Deoxyribose:
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.
Question (c)
(c)
State two differences between RNA and DNA nucleotides.
Question 3
Outline the bonding between DNA nucleotides.
Question 4
The diagram below represents a DNA nucleotide.
Identify the phosphate group and deoxyribose.
Phosphate group:
Deoxyribose:
Question 5
What is a similarity between DNA and RNA?
A
Both are polymers of nucleotides.
B
Both are composed of antiparallel strands.
C
Both contain adenine, cytosine and thymine.
D
Both contain ribose sugar.
Question 6
Draw a labelled diagram to show how four nucleotides are joined together to form a double-stranded DNA molecule with two base pairs.
Question 7
State two differences between RNA and DNA nucleotides.
Question 8
The following diagram shows a short stretch of DNA. What bases are indicated by labels Y and Z ?
Y
Z
thymine
adenine
thymine
guanine
uracil
guanine
uracil
adenine
Question 9
What allows DNA to store very large amounts of data?
A
Two strands of DNA
B
Base sequence
C
Complementary base pairing
D
Sugar-phosphate backbone
Question 10
Some yeast genes can be replaced by human genes that then continue to produce the same human proteins in the yeast cells. Which statement helps to explain this evidence?
A
The DNA of yeast and humans is identical.
B
Yeast and humans have the same number of chromosomes.
C
The genetic code is universal.
D
Yeast and humans are both eukaryotes.
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