EduNinja
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A number of diseases, such as dengue fever, are spread by mosquitoes. The incidence of this disease has increased dramatically in recent years and this has been linked with the spread of the mosquito, Aedes aegypti.

In an attempt to reduce the numbers of A. aegypti, genetically modified (GM) male mosquitoes were produced. One of the genes added to these mosquitoes, when switched on, results in the production of a protein which is toxic to mosquitoes.

In 2010, in the Cayman Islands and in Malaysia, GM male mosquitoes were released into the wild to mate with females. All the resulting offspring died in the larval stage.

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GM mosquitoes carrying the tTA gene can live and reproduce normally when fed on a diet containing an added chemical, A.

With reference to Fig. 2.1:

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suggest why there is little danger of the gene carried by these GM mosquitoes being passed to other organisms from GM mosquitoes which escape or are released into the wild.

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The polymerase chain reaction (PCR) is used to produce large quantities of DNA from a very small original sample. The main steps of one PCR method are shown in Fig. 4.1.

Fig. 4.1

Fig. 4.1

(a)

The presence of a faulty allele of the gene B R C A 2 can lead to an increased chance of developing breast cancer. There are many different faulty alleles of the gene BRCA2.

People who are considered to be at risk of breast cancer may choose to be tested for the presence of these alleles in their genomes.

A microarray can be used to test blood samples for the presence of these alleles. The microarray contains DNA probes for different faulty alleles of the BRCA2 gene.

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State the meaning of the term genome.

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Recombinant human proteins can be used to treat disease.

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Define the term recombinant DNA.

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To identify the function of a gene, scientists can insert (add) a copy of the gene into a plasmid to create recombinant DNA. The plasmid is then transferred into a host bacterium to express the gene.

(a)

Define recombinant DNA.

One plasmid used by scientists for this purpose is pIRES2-EGFP.
Fig. 5.1 shows the main features of pIRES2-EGFP.

Fig. 5.1

Fig. 5.1

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