[Maximum number: 1]

The Zika virus is a pathogen that can infect human cells.

(a)

Fig. 1.1 is a drawing of the structure of a Zika virus.

Fig. 1.1

[ 1 ]

(i)

In Fig. 1.1, structure B is a single-stranded molecule.

Suggest the name of structure B.

[ 1 ]

[Maximum number: 3]

The cells in a tissue are often at different stages of the cell cycle.

(a)

Fig. 1.1 shows cells at different stages of the cell cycle.

Fig. 1.1

[ 3 ]

(i)

Cell D in Fig. 1.1 is in interphase.

Describe the role of DNA ligase in interphase.

[ 3 ]

(a)

Semi-conservative replication of DNA occurs during interphase, before mitosis begins. Write the correct term in the spaces provided to complete each of statements A to D.

The DNA double helix unwinds and is separated into two template strands when bonds holding the two strands together are broken.

One of the template strands of DNA is copied in fragments. The enzyme is required to join the fragments together to form a continuous strand of DNA.

Complementary DNA nucleotides are added to the template strands, catalysed by the enzyme .

are regions of repeating nucleotide sequences at the ends of chromosomes that allow the continued replication of DNA, without the loss of genes.

[ 4 ]

[Maximum number: 4]

Fig. 1.1 is a diagram showing the structure of a section of a DNA molecule.

Fig. 1.1

(a)

Draw a circle around one monomer of DNA in Fig. 1.1.

[ 1 ]

(b)

Name the two bases forming the base pair at X in Fig. 1.1 and give a reason for your answer. bases reason

[ 2 ]

(c)

The statements 1-5 describe events that occur during DNA replication.

1 DNA polymerase forms a phosphodiester bond
2 DNA double helix forms
3 hydrogen bonds break
4 hydrogen bonds form
5 two strands of the double helix separate
Write the numbers 1 to 5 in the spaces below to show the order in which these events occur. The first one has been done for you.
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3
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[ 1 ]

[Maximum number: 1]

Protein production involves a complex sequence of events and a number of cell structures.

(a)

One example of protein modification is the removal of the first amino acid, methionine, from a newly formed polypeptide chain to make a functioning protein.

[ 1 ]

(i)

The DNA nucleotide sequence that specifies the amino acid methionine is TAC.

State the mRNA nucleotide sequence that is complementary to the DNA sequence for methionine.

[ 1 ]

(a)

ATP and NAD both play important roles in respiration. Both compounds are nucleotides.
Fig. 1.1 represents the molecular structures of ATP and NAD.

Fig. 1.1

Using Fig. 1.1, compare the structures of ATP and NAD.

[ 3 ]

(a)

ATP and coenzyme A both play important roles in respiration.
Fig. 1.1 represents the molecular structure of coenzyme A.

Fig. 1.1

[ 2 ]

(i)

With reference to Fig. 1.1, state two structural similarities between coenzyme A and ATP.

1

2

[ 2 ]

[Maximum number: 1]

Which letter identifies cell structures where semi-conservative replication of DNA occurs?

[Maximum number: 1]

ATP molecules are synthesised in mitochondria.
Which sugar is found in these ATP molecules?

deoxyribose

fructose

glucose

pentose

[Maximum number: 1]

Which types of RNA are found in both prokaryotic and eukaryotic cells?

mRNA

rRNA

tRNA

key

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