A-Level Biology: Genome Projects, Screening and Gene Therapy

Gene technology questions at A level rarely stop at 'what does PCR do'. They ask what sequencing a genome actually tells you, which cloning method suits a job, and what a screening result means for a family. This material covers those applications; the basic tools (PCR cycles, genetic fingerprinting, marker genes, RNA interference) are practised in the gene expression material of this category.

The first part is about genome projects. You explain why the genome of a simple organism lets you work out its proteome fairly directly, while in complex organisms non-coding DNA, introns and regulatory genes make the link much harder, and how sequencing a pathogen helps identify antigens for vaccines. The second part compares the ways of getting and multiplying a gene: making cDNA from mRNA with reverse transcriptase (and why that suits production in bacteria), cutting fragments with restriction endonucleases, and then amplifying them either in vivo, in transformed host cells, or in vitro by PCR. The questions weigh speed, accuracy, the need for living cells and the ability to make the protein itself.

The final part turns to medicine. Labelled DNA probes and hybridisation are used to screen for alleles of inherited disorders and for mutated oncogenes; the results feed into genetic counselling and personalised medicine, where treatment is matched to a patient's genotype. Gene therapy is treated in detail: somatic versus germ-line therapy, delivery with viral vectors or liposomes, why somatic therapy has to be repeated, and the ethical questions each raises.

The material offers a multiple-choice quiz with explained answers, a flashcard deck of the key terms, a printable written-work sheet of eight open questions (explanations, comparisons and evaluations) answered by hand and checked, and an oral exam in which an examiner asks one question at a time and gives feedback at the end.

The content is based on the genome projects and gene technologies content of the DfE A level biology subject content, as taught in current exam-board specifications (for example AQA topic 8, genome projects and gene technologies). It is practice material and does not replace your own board's specification.

• Explain why the proteome of a simple organism is easier to predict from its genome than that of a complex organism
• Describe how DNA fragments are produced using reverse transcriptase and restriction endonucleases
• Compare in vivo and in vitro amplification of DNA
• Explain how labelled DNA probes are used in genetic screening
• Describe the roles of genetic counselling and personalised medicine
• Compare somatic and germ-line gene therapy, including delivery methods and ethical issues

Practice material written by Zestly, based on the DfE A level biology subject content (genome projects and gene technologies).