Microarrays, bioinformatics and GMO risks and benefitsEdexcel International A Level Biology: Mind map

Exam questions on Microarrays, bioinformatics and GMO risks and benefits

1. A researcher wants to know which genes are active in a breast tumour compared with healthy breast tissue. mRNA is extracted from each tissue and used to make cDNA labelled with a fluorescent dye: red for the tumour sample and green for the healthy sample. The labelled samples are mixed and added to a microarray, a slide on which each spot contains many copies of single-stranded DNA from one known human gene. After washing, the colour of each spot is recorded.
   Explain why the researcher extracts mRNA, rather than DNA, from the tissues to find which genes are active.2 marks
2. A laboratory sequences the whole genome of a newly discovered soil bacterium. The team uses computer software and online databases of known gene sequences to look for genes similar to known antibiotic-resistance genes.
   Suggest how bioinformatics could help the laboratory decide whether the bacterium may be resistant to antibiotics, and why this is quicker than testing the bacterium in the laboratory.2 marks
3. In a three-year field trial a GM maize variety carrying a gene from Bacillus thuringiensis for a toxin that kills the caterpillars of the maize borer was compared with a non-GM variety. The mean yield of the GM maize was 11.2 t ha⁻¹ and of the non-GM maize 9.8 t ha⁻¹. Farmers growing the non-GM maize sprayed insecticide on average 3.1 times per season; those growing the GM maize sprayed on average 0.5 times per season.
   Explain how the use of the GM maize benefits farmers and the environment.3 marks