OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What defines a gene?

1. A unit of heritable information for traits

2. Instructions for making proteins

3. A type of RNA molecule

4. A physical location on a chromosome

The correct answer is: Instructions for making proteins

The definition of a gene encompasses various aspects of genetic information, but primarily, a gene is often understood as a segment of DNA that encodes the instructions for making proteins. This means that genes serve as templates for the synthesis of proteins through the processes of transcription and translation. When a gene is expressed, it is transcribed into messenger RNA (mRNA), which is then translated by ribosomes into a specific protein. Proteins play crucial roles in virtually all biological processes, including catalyzing metabolic reactions, providing structural support, and facilitating communication between cells. Therefore, while genes do embody heritable information that can influence traits, the more precise and commonly accepted definition emphasizes their role in directing the synthesis of proteins. This connection between DNA and protein synthesis is fundamentally important in understanding genetics and cellular function. Other options, while related to aspects of genetic information, do not wholly capture the essence of what defines a gene. For instance, while a gene can be considered a unit of heritable information, this definition is broader and does not specifically address the functional role of genes in protein production. Similarly, describing a gene simply as a type of RNA molecule or as a physical location on a chromosome fails to encompass the comprehensive role of genes in encoding the necessary instructions