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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 silvered fish. The gene codes for a growth hormone (GH). She inserted copies of this GH gene in... 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
Restriction endonucleases can be used to cut the plasmid, creating sticky ends. The GH gene can also be cut with the same enzymes to produce complementary sticky ends. Once cut, the GH gene can be inserted into the plasmid, and ligase enzymes can then be used to join the GH gene and the plasmid together, forming a recombinant plasmid.
Step 2
Suggest and explain how delayed insertion of the GH gene could produce offspring of transgenic fish without the desired characteristic.
Answer
If the insertion of the GH gene is delayed, it may result in cell division occurring before the gene is incorporated into the nuclear DNA. This could lead to some cells not receiving the gene, leading to gametes that do not carry the desired trait. Consequently, the offspring could inherit the parental traits rather than the transgenic characteristics intended from the GH gene.
Step 3
Using Table 3, what can you conclude about the effectiveness of the GH gene on the growth of zebrafish?
Answer
From the data in Table 3, we can conclude that the transgenic zebrafish with the GH gene have a significantly higher mean mass compared to the non-transgenic zebrafish. This indicates that the GH gene is effective in promoting growth in these fish, as the mean mass for transgenic zebrafish is 1.79 g, while that for non-transgenic zebrafish is only 0.68 g.
Step 4
Explain how two features of the design of this investigation helped to ensure the validity of any conclusions obtained.
Answer
Firstly, a large sample size of 2000 fertilised eggs for both transgenic and non-transgenic groups enhances the representativeness of the data, minimizing the impact of outliers. Secondly, the control group of untreated fertilised eggs allows for a direct comparison, ensuring any observed differences in growth can be attributed to the GH gene rather than external variables.