Background Information

We classify the broad spectrum of electromagnetic radiation from the sun into segments according to the effects we experience. For example, the warm sensation of sunshine on our skin is caused by invisible infrared radiation with wavelengths ranging from 700nm to 1,000,000nm (1mm). Visible light is comprised of wavelengths between 400nm (violet) and 700nm (red). Radiation with wavelengths shorter than 400nm but longer than 10nm is classified as Ultraviolet (UV) radiation. Radiation with wavelengths shorter than 10nm are classified as X-rays. Some exposure to UV radiation is necessary for humans to produce vitamin D, but a careful balance is required because X-rays and UV radiation are destructive to many biological molecules, including DNA. Fortunately, the earth’s atmosphere acts as a protective screen and filters out almost all the sun’s radiation with wavelengths shorter than 290nm. Nevertheless, the narrow UV band from 290nm to 400nm that can penetrate the atmosphere and reach the surface of the earth is capable of causing photochemical damage to DNA that can lead to skin cancer, so it is important to avoid over-exposure. As a defence against too much UV exposure, most organisms that are subject to the sun’s rays have evolved to incorporate some level of DNA repair in their cell mechanisms. This confers a limited amount of inherent UV resistance.

In this investigation, we will be focusing on DNA damage and the effect of UV light on the mutant strain of yeast, Saccharomyces cerevisiae. This strain of yeast does not incorporate all the genes necessary for the effective repair of photochemically damaged DNA. As a result, exposure to sunlight kills this strain of yeast more quickly than wild-type Saccharomyces cerevisiae.

Planning your Experimental Focus

Scientific investigations always begin with a research question that you want to answer. An effective research question is specific and can be answered by performing your research or investigation using the resources and equipment that you have available to you.

Further information about developing a research question and conducting background research can be found on page 181-184 in your textbook.

Planning your Experimental Design

Scientific investigations are undertaken using many different methodologies, or broader approach taken to test your research question or hypothesis. Methodologies include:

• Classification and identification

• Controlled experiment

• Correlational study

• Fieldwork

• Modelling

• Product, process or system development

• Simulation

These methodologies are outlined on p185 - 194 in your textbook.

Planning your Experimental Set-up

A well developed plan is integral to the success of a scientific investigation. Key questions to ask when developing your plan include:

• What is my hypothesis?

• What data will I need to collect?

• When and where will I collect the data?

• How will the data be analysed?

• What materials and equipment do I need?

• What are the independent and dependent variables?

• Have I identified all the variables that could influence my results?

• What are the possible risks to you, to other people, to the environment or to property?

Additional information about planning an experiment are outlined on page 194-199 in the textbook, including a discussion about different types of data and minimising error.

Collecting Raw Data

To determine a relationship between your variables, you need to have a large range and enough data points. A minimum of six data points is generally considered to be adequate, however, you should collect as many as reasonably possible within the time frame.

In this investigation, appropriate data include:

• Colony counts (count the number of colonies or dots of growth in one sector of the plate, then multiply by the number of sectors)

• Allocating the amount of coverage on the plate

The raw data should always be recorded directly into your logbook. 

Images of the plates from the investigation can be found at: Yeast plates 2025 

Analysing your data

Having collected your data, there is usually a number of steps you need to take to analyse it. This allows you to draw meaningful conclusions from your investigation, leading you to either support or refute the hypothesis and answer the investigation question.

At this stage it is often useful to use descriptive statistics, such as calculating measures of center and measures of spread. Visualising the data in a graph can also be useful tool for analysis. Additional information about useful statistics and methods of presenting data is outlined on page 203-205 in the textbook.

Interpreting Results

After visualising and analysing the data, it is important to consider what the results mean. This includes determining any patterns or trends and considering if this reflects a true relationship between the variables.

Page 205 - 207 in the textbook describes what to look for when interpreting results and relating these to the hypothesis, including the types of relationships that may be observed in data.

Analysis and interpretation should be recorded in your logbook. This includes completing the discussion, using the prompts at the start of your logbook.

Communicating your Results

An investigation is not complete until the research has been communicated to others. The VCE Biology study design (p21) specifies which methods you can select from to communicate your outcome. We have chosen a scientific poster as the method of communication.

You will need to include the following sections in your poster:

Title: This is the research question you developed in the planning stage.

Your name: Written under the title.

Introduction: This is a concise summary of the background information related to your experiment. The aim of the experiment and the hypothesis should also be included in this section.

Methodology: This is a simplified version of your experimental process. It should read as a overview in past tense and not a recipe. You may like to include a flow chart or simple diagram.

Results: Include your results is a scientifically accurate manner, in a clear table or graph with appropriate labels, headings and scale if appropriate. You do not need to explain your results in this section.

Discussion: This is a concise summary of the analysis and interpretation of results. Cover all sections including relationships observed, link to current theories and implications of results.

Conclusion: One or two sentences that summaries your experiment and findings. You should reference your research question, hypothesis and aim.

References: This is a list of the resources you used that directly relate to the information on your scientific poster. You should indicate which reference links with what specific piece of information. You do not need to include all of the resources in the bibliography list in your logbook, just the ones that specifically relate to the information on your poster.

Maximum word count: 600 words

More detailed information about what to include in each section is listed in the sections of a poster from the VCE Biology study design (below) and on page 209 - 211 in the textbook.