A technician prepares tissue cultures from an endangered fern. The nutrient agar and cutting blade are sterile, but the piece of fern tissue is placed on the agar immediately after removal from the parent plant.
Which change to the method would be most effective at preventing contamination?
Sterilise the agar a second time before adding the fern tissue.
Sterilise the piece of fern tissue before placing it on the agar.
Keep the cultures in the dark to stop microorganisms growing.
Rinse the cutting blade in tap water before each cut.
100 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.