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A scientist produced transgenic zebrafish - AQA - A-Level Biology - Question 9 - 2020 - Paper 1
Question 9
A scientist produced transgenic zebrafish. She obtained a gene from silverside fish. The gene codes for a growth hormone (GH). She inserted copies of this GH gene ... show full transcript
Worked Solution & Example Answer:A scientist produced transgenic zebrafish - AQA - A-Level Biology - Question 9 - 2020 - Paper 1
Step 1
Describe how enzymes could be used to insert the GH gene into a plasmid.
Answer
Enzymes known as restriction endonucleases are employed to cut the plasmid at specific locations, generating 'sticky ends'. This facilitates the insertion of the GH gene. Subsequently, ligase enzymes are used to join the GH gene to the plasmid, effectively creating 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, the fertilised egg cells may undergo cell division before the gene is integrated into the nuclear DNA. Consequently, the resulting gametes may be produced without the GH gene, leading to offspring that do not express the desired growth hormone characteristic.
Step 3
Using Table 3, what can you conclude about the effectiveness of the GH gene on the growth of zebrafish?
Answer
Based on the data in Table 3, one might conclude that there is a significant increase in growth rate among zebrafish that have been genetically modified to express the GH gene, compared to those that have not been modified. This suggests that the GH gene is effective in promoting growth.
Step 4
Explain how two features of the design of this investigation helped to ensure the validity of any conclusions obtained.
Answer
Two features that enhance the validity of the investigation are: 1) A large sample size, which ensures that the results are representative of the population, allowing for more reliable conclusions. 2) The inclusion of a control group that does not receive the GH gene, which enables comparisons to determine the specific effects of the GH gene on growth.