AQA AS Biology Paper 1 2021 Question Paper

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0 1 Figure 1 shows part of a DNA molecule.

Figure 1

0 1 . 1 Name the type of bond between:

[2 marks]

complementary base pairs

adjacent nucleotides in a DNA strand

0 1 . 2 The length of a gene is described as the number of nucleotide base pairs it contains.

Use information in Figure 1 to calculate the length of a gene containing 4.38 ×103

base pairs.

[2 marks]

Answer nm

3

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0 1 box . 3 Describe two differences between the structure of a tRNA molecule and the

structure of an mRNA molecule.

[2 marks]

1

2

0 1 . 4 In a eukaryotic cell, the structure of the mRNA used in translation is different from

the structure of the pre-mRNA produced by transcription.

Describe and explain a difference in the structure of these mRNA molecules.

[2 marks]

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4

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box 0 2 Figure 2 shows the structure of the human immunodeficiency virus (HIV).

Figure 2

0 2 . 1 Name structures A and B.

[2 marks]

A

B

0 2 . 2 Describe how HIV is replicated.

[4 marks]

6

5

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ANSWER IN THE SPACES PROVIDED 

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box 0 3 Uronema marinum is a single-celled eukaryotic organism. Figure 3 is a photograph

of U. marinum taken through an optical microscope.

Figure 3

0 3 . 1 Explain why it is not possible to determine the identity of the structures

labelled X using an optical microscope.

[2 marks]

0 3 . 2 U. marinum cells ingest bacteria and digest them in the cytoplasm.

Describe the role of one named organelle in digesting these bacteria.