2) which of the quadriceps crosses two joints? what are it’s actions?

Rectus Femoris

Explanation:

It has an action of extending the knee from a seated position.

I hope this helps, and as always, I am joyous to assist anyone at any time.

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."

it takes hundreds of years to become stable.

if you have another question lmk.