Can anyone me with anatomy and physiology? ?

What would be the result if crossing over did not happen during meiosis in humans? a. there would be less genetic variation in humans. b. parents would be more likely to look like their children. c. the human population could not reproduce. d. children would have more chromosomes.

What is the compliment dna strand to the following sequence: ttgactaggcta

Explain how scientists use geologic time to determine the age of landforms.