A student sterilises the nutrient medium and the forceps used for plant tissue culture. The student then touches the sterilised tips with bare fingers before transferring the tissue.
Which change would most directly reduce contamination?
Use larger pieces of plant tissue when transferring to the medium.
Avoid touching the forceps tips after they have been sterilised.
Increase the sugar concentration of the sterilised nutrient medium.
Keep the culture containers in brighter light after the transfer.
44 exam-style questions on Edexcel GCSE Biology 4.3 Selective breeding and genetic modification, covering 4.3.1 Selective breeding and its impact, 4.3.2 Tissue culture, 4.3.3 Genetic engineering overview, 4.3.4 Main stages of genetic engineering, 4.3.5 Advantages and disadvantages of GM organisms, 4.3.6 Agricultural solutions for a growing population, and 4.3.7 Evaluating genetic engineering and breeding. Each one has a worked solution and a mark scheme showing where the marks go.