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A scientist produced transgenic zebrafish - AQA - A-Level Biology - Question 9 - 2020 - Paper 2
Question 9
A scientist produced transgenic zebrafish. She obtained a gene from silverstripe fish. The gene codes for a growth hormone (GH). She inserted copies of this GH gen... show full transcript
Worked Solution & Example Answer:A scientist produced transgenic zebrafish - AQA - A-Level Biology - Question 9 - 2020 - Paper 2
Step 1
Describe how enzymes could be used to insert the GH gene into a plasmid.
Answer
Enzymes such as restriction endonucleases are used to cut the plasmid at specific sites, creating 'sticky ends' that allow the insertion of the GH gene, which has been prepared in a similar manner. This matching of sticky ends facilitates the ligation process, where ligase enzymes then join the GH gene and the plasmid together.
Step 2
Suggest and explain how delayed insertion of the GH gene could produce offspring of transgenic fish without the desired characteristic.
Answer
Delayed insertion of the GH gene into the nuclear DNA may result in cell division occurring before the gene is integrated. Consequently, this could lead to gametes being produced that do not contain the GH gene, resulting in offspring that lack the desired transgenic trait.
Step 3
Using Table 3, what can you conclude about the effectiveness of the GH gene on the growth of zebrafish?
Answer
The data in Table 3 shows that transgenic zebrafish have a significantly higher mean mass (1.79 g) compared to non-transgenic zebrafish (0.68 g). This suggests that the GH gene is effective in enhancing the growth of zebrafish.
Step 4
Explain how two features of the design of this investigation helped to ensure the validity of any conclusions obtained.
Answer
- A large sample size (2000 fertilised eggs for each group) enhances the representativeness and reliability of the results, reducing the impact of variation.
- The control group (2000 untreated fertilised eggs) allows for direct comparison to assess the effect of the GH gene on growth.