(HT only) In genetic engineering: • enzymes are used to isolate the…

The idea

Genetic engineering changes an organism's genotype by transferring a gene from one organism to another. First, enzymes are used to isolate the required gene from the donor DNA. The gene is then inserted into a vector, usually a bacterial plasmid or a virus. The vector carries the gene into the required cells, where it becomes part of the cell's DNA. In animals, plants and microorganisms, the gene is transferred at an early stage of development, so the organism grows and develops with the desired characteristics. For example, a human insulin gene can be inserted into a bacterial plasmid, and the bacteria then produce insulin. Because the gene is present from an early stage, every cell derived from the modified cell can carry it.

What earns the marks

• State that enzymes are used to isolate the required gene from the donor organism's DNA.
• Describe that the isolated gene is inserted into a vector, usually a bacterial plasmid or a virus.
• Explain that the vector is used to insert the gene into the required cells.
• State that genes are transferred to cells of animals, plants or microorganisms at an early stage in their development.
• Explain that early transfer means the organism develops with the desired characteristics.
• Apply the process to an example, such as inserting the human insulin gene into a bacterial plasmid so bacteria produce insulin.
• Recognise that the vector acts as a carrier and that the gene becomes part of the recipient cell's genetic material.
• Distinguish genetic engineering, which transfers a gene between organisms, from selective breeding, which chooses existing individuals to reproduce.

Common mistakes and how to put them right

• Saying the vector is the gene.

  Put it right by stating that the vector is the carrier, such as a bacterial plasmid or a virus, into which the required gene is inserted.

• Thinking the gene is added after the organism has developed.

  Put it right by stating that transfer happens at an early stage of development so the organism develops with the desired characteristics.

• Confusing genetic engineering with cloning.

  Put it right by explaining that genetic engineering transfers a gene from one organism to another, whereas cloning produces genetically identical copies.

Exam tips

• Sequence the process clearly: isolate the gene, insert it into a vector, use the vector to insert the gene into the required cells.
• Name the vector as a bacterial plasmid or a virus, and state that enzymes isolate the required gene.
• When explaining why transfer occurs early, link it directly to the organism developing with the desired characteristics.
• Use one named example, such as insulin production by genetically engineered bacteria, to show understanding of the whole process.