EduNinjaThe Zika virus is a pathogen that can infect human cells.
Fig. 1.1 is a drawing of the structure of a Zika virus.
Fig. 1.1
In Fig. 1.1, structure B is a single-stranded molecule.
Suggest the name of structure B.
DNA replication is an important event in the cell cycle.
Fig. 2.1 shows pairing between two bases, X and Y, in a DNA molecule.
Fig. 2.1
State which base, X or Y, is a pyrimidine and explain your answer.
Which statements about the nucleotide containing uracil are correct?
1 Uracil is a pyrimidine.
2 The carbohydrate is always ribose.
3 Base pairing occurs with 3 hydrogen bonds.
1, 2 and 3
1 and 2 only
1 and 3 only
2 and 3 only
What is correct for thymine?
has a single ring structure
is a pyrimidine
joins its complementary base with 3 hydrogen bonds
key
✓ = correct
incorrect
✓
✓
✓
✓
✓
x
✓
✓
Which nucleic acid bases are pyrimidines?
adenine and guanine
adenine, cytosine and thymine
cytosine, thymine and uracil
guanine, cytosine and uracil
The diagram represents a nucleotide containing thymine.
Which statements about this nucleotide are correct?
1 Thymine is a pyrimidine.
2 Base pairing occurs with two hydrogen bonds.
3 The carbohydrate can be ribose or deoxyribose.
1, 2 and 3
1 and 2 only
1 and 3 only
2 and 3 only
The diagram represents a nucleotide containing cytosine.
Which statements about this nucleotide are correct?
1 The carbohydrate could be ribose.
2 The organic base contains nitrogen.
3 Base pairing occurs with guanine.
4 Cytosine is a purine.
1, 2 and 3
1, 2 and 4
1, 3 and 4
2, 3 and 4
Which letter in the key describes uracil?
Which row represents the correct features of guanine?
has a single ring structure
is a purine
joins its complementary base via three hydrogen bonds
pairs with thymine
key
✓ = correct
not correct
✓
✓
✓
✓
✓
x
✓
✓
✓
✓