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Question Numbers: 16-25
Read the passage and answer the questions that follow:
Mosquitoes can transmit pathogens that cause many human diseases, such as malaria, yellow fever, dengue fever, chikungunya, and Zika fever. Many of these diseases can be physically devastating and even fatal. For example, according to the World Health Organization (WHO), there are over 200 million new cases of malaria per year worldwide, resulting in over 400,000 deaths, most of them children under the age of 5. Zika fever is caused by a virus transmitted to humans primarily by the bite of Aedes aegypti mosquitoes. Symptoms in infected human adults are typically mild, but if the virus infects a pregnant woman it can be transmitted to the developing fetus and affect brain development, causing a condition called microcephaly. To reduce the number of A. aegypti mosquitoes that may carry Zika virus, researchers at a biotechnology company called Oxitec have produced genetically modified (GM) A. aegypti mosquitoes that when released into the wild, mate with wild mosquitoes, and any offspring produced die before becoming adults.
The fluorescence gene is used to_________ GM mosquitoes. The lethality gene, which is more accurately called tetracycline transcriptional activator variant (or tTAV), encodes a protein that blocks transcription of several other genes that are essential to mosquito development. GM mosquito larvae that produce the tTAV protein die before reaching maturity. However, the tTAV protein cannot prevent the transcription of other genes when it is bound to the antibiotic tetracycline. Therefore, tetracycline acts as a repressor of the lethality gene, or, in other words, its antidote. In the lab, the GM mosquito larvae are reared in water containing tetracycline and develop normally into adult mosquitoes. When adult GM mosquitoes are released into the wild and breed with wild, non-GM mosquitoes, their offspring inherit the lethality gene. Without tetracycline in the environment to protect them, the offspring die.
In one study, Oxitec scientists released GM mosquitoes into a neighborhood in Brazil. Sustained release over the course of a year led to a reduction of the local Aedes aegypti population by 80% to 95% according to different measures (Carvalho et al., 2015). The scientists chose densely populated neighborhoods for their study because mosquito-borne diseases can spread most easily in areas where lots of humans and mosquitoes are present. They hypothesized that if they could reduce both the population size of the A. aegypti mosquitoes and the mosquito population density, they would reduce the probability that a person becomes infected with a pathogen spread by these mosquitoes. (An activity that shows how scientists measure mosquito density, based on data from Oxitec scientists, is available on the BioInteractive website as “Tracking Genetically Modified Mosquitoes.”)
Read the passage and answer the questions that follow:
Mosquitoes can transmit pathogens that cause many human diseases, such as malaria, yellow fever, dengue fever, chikungunya, and Zika fever. Many of these diseases can be physically devastating and even fatal. For example, according to the World Health Organization (WHO), there are over 200 million new cases of malaria per year worldwide, resulting in over 400,000 deaths, most of them children under the age of 5. Zika fever is caused by a virus transmitted to humans primarily by the bite of Aedes aegypti mosquitoes. Symptoms in infected human adults are typically mild, but if the virus infects a pregnant woman it can be transmitted to the developing fetus and affect brain development, causing a condition called microcephaly. To reduce the number of A. aegypti mosquitoes that may carry Zika virus, researchers at a biotechnology company called Oxitec have produced genetically modified (GM) A. aegypti mosquitoes that when released into the wild, mate with wild mosquitoes, and any offspring produced die before becoming adults.
The fluorescence gene is used to_________ GM mosquitoes. The lethality gene, which is more accurately called tetracycline transcriptional activator variant (or tTAV), encodes a protein that blocks transcription of several other genes that are essential to mosquito development. GM mosquito larvae that produce the tTAV protein die before reaching maturity. However, the tTAV protein cannot prevent the transcription of other genes when it is bound to the antibiotic tetracycline. Therefore, tetracycline acts as a repressor of the lethality gene, or, in other words, its antidote. In the lab, the GM mosquito larvae are reared in water containing tetracycline and develop normally into adult mosquitoes. When adult GM mosquitoes are released into the wild and breed with wild, non-GM mosquitoes, their offspring inherit the lethality gene. Without tetracycline in the environment to protect them, the offspring die.
In one study, Oxitec scientists released GM mosquitoes into a neighborhood in Brazil. Sustained release over the course of a year led to a reduction of the local Aedes aegypti population by 80% to 95% according to different measures (Carvalho et al., 2015). The scientists chose densely populated neighborhoods for their study because mosquito-borne diseases can spread most easily in areas where lots of humans and mosquitoes are present. They hypothesized that if they could reduce both the population size of the A. aegypti mosquitoes and the mosquito population density, they would reduce the probability that a person becomes infected with a pathogen spread by these mosquitoes. (An activity that shows how scientists measure mosquito density, based on data from Oxitec scientists, is available on the BioInteractive website as “Tracking Genetically Modified Mosquitoes.”)
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