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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 play a crucial role in the insertion of the GH gene into a plasmid. First, restriction endonucleases are used to cut the plasmid at specific sites, producing 'sticky ends'. These sticky ends allow for the formation of base pairs between the plasmid and the GH gene. Following this, ligase enzymes join the GH gene to the plasmid by linking their sticky ends, thereby creating a recombinant plasmid that contains the GH gene.
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 may lead to a scenario where cell division occurs before the gene is incorporated into the nuclear DNA. If fertilised egg cells undergo division prior to the transfer of the GH gene, not all cells will receive the gene during subsequent divisions. Consequently, some offspring may develop without expressing the desired growth characteristics associated with the GH gene, as they may lack the gene entirely in their somatic cells.
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, it can be concluded that the GH gene significantly enhances the growth of transgenic zebrafish compared to control groups. The results indicate a marked increase in weight, which suggests that the introduction of the GH gene improves growth rates and overall biomass in the affected populations.
Step 4
Explain how two features of the design of this investigation helped to ensure the validity of any conclusions obtained.
Answer
Two important features of the investigation's design that ensured validity include:
- A large sample size was employed, making the results more representative and reducing the potential for anomalies.
- A control group was established, allowing for comparisons between transgenic and non-transgenic zebrafish. This control enables researchers to attribute growth differences directly to the GH gene's influence, rather than external factors or random variation.