Ions are transported across plasma membranes using

Active transport.

Explanation:

To move substances or ions against a concentration or electrochemical gradient, the cell must utilize energy which is in the form of ATP during active transport.

Primary active transport, which is directly dependent on ATP, moves ions across a membrane and creates a difference in charge across that membrane.

c.) polymerase chain reaction

- "unlike the original dna fingerprinting method, dna profiling does not use restriction enzymes to cut the dna. instead it uses the polymerase chain reaction (pcr)? to produce many copies of specific str sequences. pcr is an automated procedure that generates lots of copies of a specific sequence of dna."