instruction:
In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.
question:
Question: When does exchange of dna segments happen between non-sister chromatids of homologous chromosomes? Answer: during crossing-over
answer:
Exchange of dna segments happens between non-sister chromatids of homologous chromosomes during crossing-over.

question:
Question: What forms a ketone when oxidized? Answer: secondary alcohol
answer:
Secondary alcohol forms a ketone when oxidized.

question:
Question: Which of these human activities in a forest has a positive effect on the ecosystem? Answer: Planting new trees where old ones were cut down
answer:
Planting new trees where old ones were cut down of these human activities in a forest has a positive effect on the ecosystem.