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CAIE A-Level Biology A2 19.1.7 Gene Editing By Insertion Deletion or Replacement Questions

Use real exam evidence to explain how gene editing targets specific DNA, deletes or inactivates unwanted alleles, inserts or replaces sequence and differs from plasmid-vector…

Syllabus
2028–2030
Course
Biology 9700
Level
A2

Exam points

  • Explain gene-editing specificity through a target DNA sequence that is recognised only at the intended gene or allele.
  • Apply deletion or inactivation to remove a harmful allele or gene function, then use phenotype or quantitative evidence to judge editing success and advantages.
  • Use insertion or template-directed replacement at a specific DNA site to correct a mutation or change codons, amino acids and protein function.
  • Compare gene editing with plasmid-vector engineering or gene addition using precision, single-base changes, CRISPR, marker genes and DNA ligase.

CAIE A-Level Biology A2 19.1.7 Gene Editing By Insertion Deletion or Replacement Questions question 1

[Maximum number: 3]

Traditional techniques for genetically modifying organisms use three enzymes:
- restriction endonuclease
- reverse transcriptase
- DNA ligase.

For example, these enzymes have been used to produce genetically modified (transgenic) pigs containing the GFP gene coding for green fluorescent protein, originally sourced from jellyfish.

Some of the zygotes in each group survived and after six days each had developed into a group of cells called a blastocyst.

The blastocysts were counted using a light microscope. A filter was then added to the microscope, so that only blastocysts expressing the green fluorescent protein showed up. These were counted and the results are summarised in Table 5.1.

Table 5.1

Table 5.1

State the best concentration of Cas9 nuclease and guide RNA to use to cause a deletion in the GFP gene and give reasons for your choice.

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