biology

give me short answers ( but perfect) for both questions.100-150 words each....

1)Given a choice of the types of genetic mutations discussed in class, which point and chromosomal mutations would be the least likely to cause problems for the eukaryotic organism? Explain your choice.

2)Explain in terms of cellular respiration why we need oxygen and why we exhale carbon dioxide. Is there an alternative to using oxygen? What is the alternative and is it viable option for multi-cellular aerobic organisms to survive long-term in an oxygen deficient environment?