CourseCourseConceptConceptDocsDocuments

CAIE A-Level Biology AS 6 Nucleic Acids and Protein Synthesis Questions

Practise moving between nucleotide structures, DNA replication, base sequences, transcription, translation and mutation evidence.

Syllabus
2028–2030
Course
Biology 9700
Level
AS

Covered syllabus points

6.1 Structure of Nucleic Acids and DNA Replication6.2 Protein Synthesis

Question 1

[Maximum number: 2]

In most plants, sucrose is the main sugar that is transported from sources to sinks.

Fig. 5.1 shows part of one pathway that is used in plant cells to synthesise sucrose. The enzyme sucrose synthase catalyses the transfer of glucose from UDPG (uridine diphosphate glucose) to fructose.

Fig. 5.1

Fig. 5.1

The structure of UDPG is shown in Fig. 5.2.

Fig. 5.2

Fig. 5.2

Explain why UDP can be described as a phosphorylated nucleotide.

Question 2

[Maximum number: 2]

Starch molecules are the main storage molecules in many types of cereal grain, such as the grain of the barley plant.

When the seed inside a barley grain germinates, genes coding for digestive enzymes are switched on. The enzymes that are synthesised catalyse the hydrolysis of storage molecules such as proteins and starch.

Explain what is meant by a gene.

Question 3

[Maximum number: 8]

Question (a)

(a)

Describe the process of DNA replication.

[ 5 ]

Question (b)

(b)

During DNA replication, the use of an incorrect base in the newly synthesised strand can lead to a mutation.

[ 3 ]

Question (i)

(i)

A transversion event is where a pyrimidine is used in the newly synthesised strand instead of a purine, or the other way round.

Name the two possible bases that could be used instead of cytosine in a transversion event.

[ 1 ]

Question (ii)

(ii)

A transition event is where an incorrect purine is used or an incorrect pyrimidine is used. Suggest why transversion events are less likely to occur than transition events.

[ 2 ]

Question 4

[Maximum number: 8]

Cathelicidin LL-37 is a cell signalling compound that stimulates many different cells in humans. One role of cathelicidin LL-37 is stimulating the production of endothelial cells in the formation of capillaries during wound healing.

Question (a)

(a)

Mutations of DNA base sequences in a gene can affect the primary structure of proteins.

Use the information in Table 5.1 and Table 5.2 to suggest the effect on the primary structure of cathelicidin LL-37 of:

[ 5 ]

Question (i)

(i)

the substitution of the base T with the base A in the middle of the triplet at position 5

[ 1 ]

Question (ii)

(ii)

the deletion of base T in the triplet at position 2

[ 2 ]

Question (iii)

(iii)

the insertion of base G between bases G and T in the triplet at position 3 .

[ 2 ]

Question (b)

(b)

The genetic code is described as universal.

Explain why the genetic code is described as universal.

[ 1 ]

Question (c)

(c)

Use Table 5.2 to explain why some mutations have no effect on the primary structure of a protein.

[ 2 ]
All question bank results loaded