Observed numbers of mosquitoes by kdr genotype +/+ +/r r/r A. gambiae Pre-2006 3 5 2 2006 8 8 7 Post-2006 3 3 57 Hybrids 2006 10 7 0 A. coluzzii Pre-2006 226 0 0 2006 70 7 0 Post-2006 79 127 94
Malaria is a leading cause of human illness and mortality worldwide, with 200 million people infected and 600,000 deaths each year. In the 1960s, the incidence of malaria was reduced owing to the use of insecticides that killed mosquitoes in the genus Anopheles, which transmit the disease from person to person. But today, mosquitoes are becoming resistant to insecticides--causing a resurgence in malaria.
In this exercise, you will investigate whether alleles encoding resistance to insecticides have been transferred between closely related species of Anopheles. To find out whether transfers have occurred, you will analyze DNA results from two species of mosquitoes that transmit malaria (Anopheles gambiae and A. coluzzii) and from A. gambiae × A. coluzzii hybrids.
Resistance to DDT and other insecticides in Anopheles is affected by a sodium channel gene, kdr. The allele r of this gene confers resistance, while the wild type (+/+) genotype is not resistant. Researchers sequenced the kdr gene from mosquitoes collected in Mali during three time periods: pre-2006, 2006, and post-2006. A. gambiae and A. coluzzii were collected during all three time periods, but their hybrids only occurred in 2006, the first year that insecticide-treated bed nets were used to reduce the spread of malaria. A likely explanation is that the introduction of the treated bed nets may have briefly favored hybrid individuals, which are usually at a selective disadvantage.
Use the data provided in the table to calculate the percent frequency of the +/+ genotype in A. gambiae over time (from pre-2006 to post-2006). Note that “frequency” refers to the proportional representation of an allele or genotype in a population.
Malaria is a leading cause of human illness and mortality worldwide, with 200 million people infected and 600,000 deaths each year. In the 1960s, the incidence of malaria was reduced owing to the use of insecticides that killed mosquitoes in the genus Anopheles, which transmit the disease from person to person. But today, mosquitoes are becoming resistant to insecticides--causing a resurgence in malaria.
In this exercise, you will investigate whether alleles encoding resistance to insecticides have been transferred between closely related species of Anopheles. To find out whether transfers have occurred, you will analyze DNA results from two species of mosquitoes that transmit malaria (Anopheles gambiae and A. coluzzii) and from A. gambiae × A. coluzzii hybrids.
Resistance to DDT and other insecticides in Anopheles is affected by a sodium channel gene, kdr. The allele r of this gene confers resistance, while the wild type (+/+) genotype is not resistant. Researchers sequenced the kdr gene from mosquitoes collected in Mali during three time periods: pre-2006, 2006, and post-2006. A. gambiae and A. coluzzii were collected during all three time periods, but their hybrids only occurred in 2006, the first year that insecticide-treated bed nets were used to reduce the spread of malaria. A likely explanation is that the introduction of the treated bed nets may have briefly favored hybrid individuals, which are usually at a selective disadvantage.
Use the data provided in the table to calculate the percent frequency of the +/+ genotype in A. gambiae over time (from pre-2006 to post-2006). Note that “frequency” refers to the proportional representation of an allele or genotype in a population.
1. What is the percent frequency of the +/+ genotype in A. gambiae prior to 2006?
2. What is the percent frequency of the +/+ genotype in A. gambiae in 2006?
3. What is the percent frequency of the +/+ genotype in hybrids in 2006?
4. What is the percent frequency of the +/+ genotype in A. gambiae after 2006?
* these are the different parts to one question, the paragraph above is background information.
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