Genetic engineering may often involve the transfer of a gene into an organism. Some species of Anopheles mosquitoes, such as Anopheles stephensi, transmit malaria. Scientists have created genetically engineered $$$A$$$. stephensi mosquitoes in an attempt to reduce the spread of malaria. A gene called tTav was constructed by scientists and transferred into the eggs of $$$A$$$. stephensi. - tTav consists of DNA sequences from a bacterium, Escherichia coli, and herpes simplex virus, which is a DNA virus. - The gene codes for tTav protein, which stops the expression of genes that are essential to mosquito development. - Genetically engineered $$$A$$$. stephensi do not survive beyond the larval stage and therefore do not develop into adults. - A chemical called tetracycline can stop the action of the tTav protein. Male genetically engineered $$$A$$$. stephensi were released into the wild to breed with females. Their offspring had the tTav gene. (i) Describe how the tTav gene could have been synthesised and transferred into the eggs of $$$A$$$. stephensi. . . . . . . . (ii) Suggest how the tTav protein prevents the expression of other genes in $$$A$$$. stephensi. . (iii) Genetically engineered $$$A$$$. stephensi larvae were exposed to tetracycline in the laboratory. Suggest why A. stephensi larvae were exposed to tetracycline in the laboratory. .

Biology

IGCSE&ALevel

CAIE

Exam No：9700_s25_qp_44 Year：2025 Question No：5(b)

Answer:

Knowledge points:

16.3.1 describe the differences between structural genes and regulatory genes and the differences between repressible enzymes and inducible enzymes

16.3.2 explain genetic control of protein production in a prokaryote using the lac operon (knowledge of the role of cAMP is not expected)

16.3.3 state that transcription factors are proteins that bind to DNA and are involved in the control of gene expression in eukaryotes by decreasing or increasing the rate of transcription

16.3.4 explain how gibberellin activates genes by causing the breakdown of DELLA protein repressors, which normally inhibit factors that promote transcription

19.1.1 define the term recombinant DNA

19.1.10 outline how microarrays are used in the analysis of genomes and in detecting mRNA in studies of gene expression

19.1.11 outline the benefits of using databases that provide information about nucleotide sequences of genes and genomes, and amino acid sequences of proteins and protein structures

19.1.2 explain that genetic engineering is the deliberate manipulation of genetic material to modify specific characteristics of an organism and that this may involve transferring a gene into an organism so that the gene is expressed

19.1.3.1 extracted from the DNA of a donor organism

19.1.3.2 synthesised from the mRNA of a donor organism

19.1.3.3 synthesised chemically from nucleotides

19.1.4 explain the roles of restriction endonucleases, DNA ligase, plasmids, DNA polymerase and reverse transcriptase in the transfer of a gene into an organism

19.1.5 explain why a promoter may have to be transferred into an organism as well as the desired gene

19.1.6 explain how gene expression may be confirmed by the use of marker genes coding for fluorescent products

19.1.7 explain that gene editing is a form of genetic engineering involving the insertion, deletion or replacement of DNA at specific sites in the genome

19.1.8 describe and explain the steps involved in the polymerase chain reaction (PCR) to clone and amplify DNA, including the role of Taq polymerase

19.1.9 describe and explain how gel electrophoresis is used to separate DNA fragments of different lengths

19.3.1 explain that genetic engineering may help to solve the global demand for food by improving the quality and productivity of farmed animals and crop plants, using the examples of

19.3.2 GM salmon, herbicide resistance in soybean and insect resistance in cotton

19.3.3 discuss the ethical and social implications of using genetically modified organisms (GMOs) in food production

Answer:

Knowledge points:

Solution:

Related Question