Variation: Students should be able to describe simply how the genome and its interaction with the environment influence the development of the phenotype of an organism.

The idea

The genome is the full set of genetic material an organism inherits. Genes code for proteins, and these proteins help build and control the cell, so the genome sets the potential range of features an organism can develop. The phenotype is the observable characteristics that actually appear. Environment means everything the organism experiences, such as diet, exercise, temperature, light and lifestyle. Phenotype often results from both: genes give a range, and the environment decides where within that range the organism falls. For example, a person may inherit tallness genes, but a poor diet in childhood can limit final height. Similarly, identical plant cuttings grown in bright light and in shade show different leaf size and colour. Describing simply means stating that phenotype depends on genetic information interacting with environmental factors, and giving a clear example.

What earns the marks

• States that the genome is the complete genetic material of an organism and that genes code for proteins that influence characteristics.
• Explains that the phenotype is the observable characteristics of an organism, resulting from the interaction of genetic information with environmental factors.
• Uses a valid example, such as height being influenced by inherited genes and by diet, or leaf colour being influenced by genes and light intensity.
• Recognises that genes set a potential range for a characteristic while the environment determines where within that range the organism develops.
• Distinguishes inherited genetic material from environmental influences when describing a named characteristic.
• Applies the idea to a familiar organism, for example identical twins or cloned plants, to show that shared genomes can still produce different phenotypes.

Common mistakes and how to put them right

• Saying the environment changes genes.

  Put it right by explaining that the environment affects how genes are expressed and how the organism develops, not the DNA base sequence itself.

• Treating phenotype as entirely genetic.

  Put it right by stating that most characteristics result from both genetic and environmental contributions.

• Confusing genome with phenotype.

  Put it right by defining the genome as the inherited genetic material and the phenotype as the observable characteristics that develop.

Exam tips

• Define genome and phenotype briefly before explaining their interaction, so the examiner can see both terms used accurately.
• Include one named characteristic and state one genetic influence and one environmental influence on it.
• Use command words carefully: describe means give a clear account, so link cause and effect rather than listing facts.