Question

question 4
how are viruses able to infect cells?
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question 5
what have the developments in the history of metagenomics contributed to the understanding of?
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Explanation:

For Question 4: Viruses have surface - proteins that can bind to specific receptor molecules on the host cell surface. Once bound, the virus can enter the cell through processes like endocytosis or membrane fusion.
For Question 5: Metagenomics developments have contributed to understanding microbial communities in various environments, including their functions, diversity, and interactions. It has allowed for the study of unculturable microorganisms and their roles in ecosystems, human health, and more.

Answer:

Question 4: Viruses bind to specific cell - surface receptors and then enter via endocytosis or membrane fusion.
Question 5: Microbial communities, their functions, diversity, and interactions in different environments.