[Maximum number: 3]

Carbonic anhydrase is a globular protein found in red blood cells.

(a)

A protein such as carbonic anhydrase is coded for by a gene. A gene forms part of a DNA molecule.

Fig. 3.1 is a diagram of a small section of a DNA molecule.

Fig. 3.1

[ 3 ]

(i)

Identify the base X and state the evidence in Fig. 3.1 that supports this identification.
base X
evidence from Fig. 3.1

[ 3 ]

[Maximum number: 3]

Fig. 4.1 shows the two base pairs in a DNA molecule.

Fig. 4.1

(a)

Name the bases labelled J and K and the bond labelled L.

J

K

L

[ 3 ]

[Maximum number: 1]

Which row represents the correct features of the nitrogenous base adenine?

has a single ring structure

is a purine

joins its complementary base by three hydrogen bonds

pairs with thymine

key

✓ = true

x= false

✓

$\chi$

✓

$\chi$

✓

$\chi$

✓

Which diagram shows a correct ring structure and named nucleic acid base?
A
D

adenine

cytosine
C
C

thymine

uracil

[Maximum number: 1]

The diagram shows part of a DNA molecule.

Which labels represent purines?

1 and 2

2 and 4

3 and 1

4 and 3

[Maximum number: 1]

Which statements about complementary base pairing are correct?
1 Purines and pyrimidines are different sizes.
2 It occurs during translation.
3 The base pairs are of different length.
4 Uracil forms two hydrogen bonds with adenine.

1, 2 and 3 only

1, 2 and 4 only

1, 3 and 4 only

2, 3 and 4 only

[Maximum number: 1]

Which statements are correct?
1 Adenine and cytosine are both purines.
2 The DNA nucleotide containing adenine is different from the RNA nucleotide containing adenine.

3 Purines only form base pairs with pyrimidines.

1, 2 and 3

1 and 2 only

1 and 3 only

2 and 3 only

[Maximum number: 1]

The diagram represents a nucleotide containing guanine.

Which statements about this nucleotide are correct?
1 The carbohydrate can be ribose or deoxyribose.
2 Base pairing occurs with three hydrogen bonds.
3 Guanine is a purine.

1, 2 and 3

1 and 2 only

1 and 3 only

2 and 3 only

[Maximum number: 1]

Which row correctly describes adenine?

complementary base

component on nucleotide strand it is attached to

ring structure

thymine

deoxyribose

double

thymine

phosphate

single

uracil

phosphate

double

uracil

ribose

single

[Maximum number: 1]

Which statements about complementary base pairing are correct?
1 It occurs during translation.
2 Purines and pyrimidines are the same size.
3 The base pairs are of equal length.
4 Uracil forms three hydrogen bonds with adenine.

1 and 2 only

1 and 3 only

2 and 3 only

3 and 4 only