Explain why crossing-over gives us so much genetic variation (differences in organisms).

well, you see. the answer to your question is quite simple. the thing that is big, powerful, and over 9,000 is your mom.

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.

b tumor cells have a cell wall instead of a membrane

explanation:

tumor cells different from normal cells because tumor cells have a cell wall instead of a membrane.