Evaluating Data about Genetic Expression (AQA A Level Biology): Revision Note

Genetic & environmental factors

Interpreting data on gene expression

• Gene expression refers to the process by which genetic information is used to synthesise proteins or functional RNA molecules

• Investigations into gene expression often involve measuring levels of mRNA or proteins under different conditions to determine how genes are regulated

• Common types of data include:

  • mRNA concentrations, measured using techniques such as RT-PCR or microarrays

    • Higher mRNA or protein levels usually indicate increased gene expression.

  • protein levels, detected through methods like ELISA

  • comparative data, showing gene expression in different cell types, tissues, or experimental conditions

RNA analysis

• RNA analysis is important with regard to gene expression

• From the outside, most cells look almost identical, with the same DNA in their nucleus; however, they are most likely expressing different genes

• When a cell expresses a gene, RNA is produced by transcription

• The RNA present in a cell can be analysed, and scientists can match the RNA present in a cell to specific genes

  • In this way, they can work out which genes are being expressed in that specific cell

• RNA analysis can be used to find the function of a cell and to determine the differences between cells in a healthy person and a patient with a specific illness

  • For example, the genes responsible for tumour formation can be detected by analysing which genes have been over-expressed within a cancer cell

  • This can lead to the discovery of drugs that block the expression of these genes

Evaluating genetic and environmental influences on phenotype

• A phenotype is the observable characteristic of an organism, resulting from the interaction between its genotype and the environment

• The relative contribution of genetic and environmental factors to phenotype can be assessed using various types of data

  • Twin studies: Monozygotic twins share identical genotypes; differences in phenotype suggest environmental influence

  • Adoption studies: Comparisons between adopted children and their biological vs adoptive families help isolate genetic and environmental contributions

  • Environmental manipulation experiments: When genetically identical organisms show phenotypic variation due to environmental differences, the role of environment is emphasised

• Evaluation of data should consider:

  • The strength and direction of correlations between variables

  • Whether results suggest causation or merely association

  • The extent to which confounding variables have been controlled

• Both genetic and environmental influences often contribute to phenotype in complex and interacting ways

  • Data analysis should reflect this by considering multiple factors and acknowledging the limitations of the evidence presented