In chemical reactions, atoms are a) created. b) rearranged. c) destroyed. d) neutralized.

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

Plz ! a scientist wants to produce a cow that makes a particular human protein in it’s milk the desired protein causes blood to clot and can be used to treat hemophilia (a blood clotting disorder). which of the following would be best for the scientist to use? a. genetic crosses. b. cloning. c. selective breeding. d. genetic engineering.

Why has two different alleles for the same trait?