How many base pairs are in a full turn or twist of a dna molecule

Restriction enzymes are used in making recombinant dna. describe the role restriction enzymes perform when constructing recombinant dna.

What environmental cues and landmarks do the geese use to determine the timing and direction of their migration over the mountains? how do they find their way?

In which of the following relationships is one organism always benefited while the other organism is always harmed