Question

why might genetically engineering a crop to be herbicide resistant result in producing weeds that are herbicide resistant?
the dna in herbicide resistant crops does not affect insects
the weeds that are not affected by the herbicide are able to reproduce
insects that are not affected by the herbicide can pollinate new species of weeds
the weeds will become tolerant to the herbicide through repeated exposure.

Explanation:

When a crop is genetically engineered to be herbicide - resistant, herbicides are used to kill weeds. Weeds that have a natural resistance (due to genetic variation) to the herbicide will survive. Since they survive, they can reproduce. Over time, through natural selection (the herbicide acts as a selective pressure), the proportion of herbicide - resistant weeds in the population will increase.

• Option 1: The question is about weeds, not insects. So this option is not relevant.
• Option 2: If weeds are not affected by the herbicide (because of their genetic makeup), they can reproduce. This is in line with the process of natural selection leading to more herbicide - resistant weeds.
• Option 3: Pollination by insects is not the main mechanism for the development of herbicide - resistant weeds in this context. The key is the survival and reproduction of herbicide - resistant weeds.
• Option 4: Tolerance through repeated exposure is not the same as genetic resistance. Genetic resistance is heritable, while tolerance (a non - genetic, physiological change) may not be passed on to offspring in the same way as a genetic trait.

Answer:

B. The weeds that are not affected by the herbicide are able to reproduce.