ConceptConceptDocsDocuments

CAIE A-Level Biology 6.1.3 Cytosine, Thymine and Uracil

Practise identifying single-ring cytosine, thymine and uracil from molecular diagrams, selecting DNA or RNA context and assigning the correct complementary purine.

Syllabus
2028–2030
Course
Biology 9700
Level
AS

Exam points

  • classify cytosine, thymine and uracil as pyrimidine bases with one ring
  • use thymine for DNA and uracil for RNA while recognising cytosine in both
  • pair cytosine with guanine and thymine or uracil with adenine as appropriate

6.1.3—Pyrimidines (cytosine, thymine, uracil) question 1

[Maximum number: 1]

The diagrams show the chemical structure of four bases.

1

1

2

2

3

3

4

4

Which diagrams show thymine and cytosine?

A

1 and 2

B

1 and 4

C

2 and 3

D

3 and 4

All question bank results loaded