Malaria is a leading cause of human illness and mortality worldwide, with 200 mi

Question

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.

**Based on these data alone, which of the following conclusions is consistent with the observed changes in genotypic frequency for A. gambiae and A. coluzzii?**

Select all that apply The r allele was present in A. gambiae before 2006 and increased over time because individuals with the r allele are resistant to insecticides and pass their resistant genes to new generations The rallele was not present in A. coluzzi before 2006, but was present in A. coluzzi populations after hybrid individuals carrying the rallele were observed in 2006. This suggests that A. gambiae × A. co/uzzi. hybrids mated with A. coluzzii individuals, leading to the transfer of the adaptive allele r into A. coluzzii populations O The r allele was present in both A. gambiae and A. coluzzii before 2006 so the impact of hybridization on the transfer of the rallele cannot be assessed. Submit Request Answer

Explanation / Answer

Select ALL that apply

Answer:

The r allele was present in A. gambiae before 2006 and increased over time because individuals with the r allele are resistant to insecticides and pass their resistant genes to new generations

The r allele was not present in A. coluzii before 2006, but was present in A. coluzzii populatios after hybrid individuals carrying the r allele were observed in 2006. This suggests that A. gambiae x A. coluzzii hybrids mated with A. coluzzii individuals, leading to the transfer of the adaptive r alele into A. coluzzii populations.

So two options are the answer

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