In the mid-1960s, DDT was widely used as an insecticide against mosquitoes - VCE - SSCE Biology - Question 23 - 2010 - Paper 1
Question 23
In the mid-1960s, DDT was widely used as an insecticide against mosquitoes. The sensitivity to insecticide in mosquitoes is determined by a single gene that has two ... show full transcript
Worked Solution & Example Answer:In the mid-1960s, DDT was widely used as an insecticide against mosquitoes - VCE - SSCE Biology - Question 23 - 2010 - Paper 1
Step 1
A. when spraying levels declined, heterozygous advantage occurred.
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Answer
The graph shows an increase in the percentage of heterozygous mosquitoes during periods of declining DDT spraying. This suggests that the heterozygous condition provides a selective advantage when DDT levels are low.
Step 2
B. there were no alleles for sensitivity present in the population in 1967.
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Answer
Analysis of the graph indicates that the percentage of homozygous sensitive mosquitoes was very low in 1967, suggesting that sensitivity alleles were not present in significant numbers.
Step 3
C. the alleles for resistance was equal to the number for sensitivity in 1966.
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Answer
In 1966, the graph indicates that the allele frequencies were almost balanced, suggesting that the number of resistant alleles was approximately equal to the number of sensitive alleles.
Step 4
D. the homozygous resistant genotype was unable to produce offspring at low spraying levels.
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Answer
The graph indicates that the homozygous resistant genotype's frequency decreased as DDT spraying levels dropped, implying that their reproductive success was compromised in those conditions.
