A-Level · Biology · AQA · Mark scheme decoded

AQA A-Level Biology: Sequencing Projects and Genome Analysis — mark scheme explained

Machine-verifiedchecked against the AQA A-Level Biology specificationlast verified 3 July 2026

The short answer

The field of genomics has revolutionized our understanding of biological systems by allowing us to read the complete genetic information (genome) of various organisms, including humans. This section delves into how sequencing projects have advanced our knowledge of genomes and proteomes, their applications, and the challenges posed by complex organisms.

The question

Explain why simpler organisms have a more straightforward relationship between their genome and proteome.

[Paraphrased for study — not reproduced from any exam paper.]

4 marks

Mark scheme, decoded

How the examiner actually awards the marks on this topic.

Gradora's own decode of the marking approach — not the exam board's published mark scheme.

How marks are awarded

For explanation questions, marks are typically awarded for providing a detailed description that includes relevant principles and relationships. For comparison questions, marks are given for identifying both similarities and differences accurately. For descriptive questions, marks are awarded for giving a clear and concise account of the process or phenomenon. For discussion questions, marks are given for examining and interpreting information to draw well-supported conclusions.

What the command words demand

Explain: Provide a detailed description of the concept, including relevant principles and relationships.
Compare: Identify similarities and differences between two or more concepts or processes.
Describe: Give a clear and concise account of a process, structure, or phenomenon.
Discuss: Examine and interpret information to draw conclusions about a topic.

Model answer

A full-mark response to the question above, worked through step by step.

Timing: Allocate approximately 5-7 minutes per question to ensure you have enough time to carefully read the problem, provide detailed answers, and check your work.

Define simpler organisms.1 mark
Simpler organisms, such as bacteria and some viruses, have smaller genomes with fewer non-coding regions and regulatory elements.
Explain the impact of fewer non-coding regions.1 mark
With fewer non-coding regions, the genetic code can be more directly translated into protein sequences.
Discuss the role of regulatory elements.1 mark
Simpler organisms have fewer regulatory genes, which means gene expression is less complex and easier to predict.
Summarize the relationship between genome and proteome in simpler organisms.1 mark
In simpler organisms, the relationship between the genome and proteome is more straightforward because the genetic code can be directly inferred from the DNA sequence.

Final answer: Simpler organisms have a more straightforward relationship between their genome and proteome because they have fewer non-coding regions and regulatory elements. This allows for a direct translation of the genetic code into protein sequences, making it easier to determine the proteome.

Work through every step correctly and you earn all 4 marks.

Another worked example

Describe two applications of determining the proteome in simpler organisms.

3 marks

Identify one application.1 mark
One application is identifying potential antigens for vaccine development. By understanding the proteome of pathogens, scientists can identify proteins that trigger an immune response and use them to develop vaccines.
Identify another application.1 mark
Another application is drug discovery. Knowledge of the proteome can help in identifying new drug targets and developing more effective treatments for various conditions.
Summarize both applications.1 mark
Determining the proteome in simpler organisms has practical applications, including identifying potential antigens for vaccine development and aiding in drug discovery.

Final answer: Two applications of determining the proteome in simpler organisms are identifying potential antigens for vaccine development and aiding in drug discovery.

Work through every step correctly and you earn all 3 marks.

Common mistakes

Confusing genome with proteome.
Why it happens: Students sometimes mix up the definitions of genome and proteome, leading to incorrect answers in questions involving these concepts.
Fix: Remember that the genome is the entire set of genetic material (DNA), while the proteome is the complete set of proteins expressed by a genome, cell, tissue, or organism at a particular time.
Failing to appreciate the complexity introduced by non-coding DNA in complex organisms.
Why it happens: Students may not fully understand the role of non-coding DNA and its impact on gene expression, leading to oversimplified explanations.
Fix: Practice explaining the significance of non-coding DNA in complex organisms, emphasizing its regulatory functions and the additional studies required to understand gene expression and protein function.
Misunderstanding the role of regulatory genes in complex organisms.
Why it happens: Students may not grasp how regulatory genes control gene expression, leading to incomplete or incorrect explanations.
Fix: Review the concept of regulatory genes and their function in controlling when and where specific genes are expressed. Emphasize that this adds another layer of complexity to the relationship between the genome and proteome.
Overlooking the practical applications of determining the proteome in simpler organisms.
Why it happens: Students may not fully appreciate the real-world applications, such as vaccine development and drug discovery, leading to vague or incomplete answers.
Fix: Practice providing specific examples of how determining the proteome can be applied in fields like vaccine development and drug discovery. Emphasize the importance of these applications in biological research.
Failing to explain the evolution of sequencing technologies and their impact on genomics research.
Why it happens: Students may not fully understand the advancements in sequencing methods and their significance, leading to incomplete or incorrect explanations.
Fix: Review the different generations of sequencing technologies, such as Sanger sequencing, next-generation sequencing (NGS), and third-generation sequencing. Emphasize how these advancements have made genome sequencing faster, more accurate, and more cost-effective, opening up new avenues for research and applications.
Confusing the relationship between the genome and proteome in simpler versus complex organisms.
Why it happens: Students may not fully grasp the differences in complexity between simpler and more complex organisms, leading to oversimplified or incorrect comparisons.
Fix: Practice comparing the relationship between the genome and proteome in simpler and complex organisms. Emphasize the straightforward nature of this relationship in simpler organisms due to fewer non-coding regions and regulatory elements, and the added complexity in complex organisms due to significant amounts of non-coding DNA and regulatory genes.

Where the marks go

The question types you’ll meet on this topic and the marks each one carries — so you know what to expect and where to focus.

Question type	What you’re asked to do	Marks
Genome And Proteome	Explain why simpler organisms have a more direct genome-to-proteome relationship.	4
Proteome Applications	State two practical uses of determining the proteome in simpler organisms.	3
Explain Genome-Proteome Link	Explain why genome sequence alone cannot accurately predict the range of proteins produced.	4
Compare Genome And Proteome	Compare how genome relates to proteome in simple organisms versus complex organisms, noting similarities and differences.	5
Total across these question types		16

Question types and mark tariffs are Gradora’s guidance based on how this topic is typically examined — not the board’s official paper structure.