20. What do scientists use to provide evidence that the earth has a solid inner core and a liquid outer core?
(1 Point)
A) drilling into the mantle
B)seismic wave
C) radar
D)x-rays
21. The layer of the atmosphere closest to the surface of the earth is called the
(1 Point)
A) Stratosphere
B)exosphere
C)mesosphere
D) troposphere

Assume that you are interested in separating short (200-400 bp) dna molecules from a pool of longer molecules in the 10,000-20,000 nucleotide range. you have two recipes for making your polyacrylamide gels: one recipe uses 1.5 percent agarose and would be considered a “hard gel,” while the other uses 0.5 percent agarose and would be considered a loose gel. which gel should you use to separate the short (200-400 bp) dna molecules from a pool of longer molecules in the 10,000-20,000 nucleotide range?