In gel electrophoresis, dna fragments move across a gel. what causes them to move?

Because each DNA molecule is negatively charged, it can be pulled through the gelby an electric field. Small DNA molecules move more quickly through the gel than larger DNA molecules. The result is a series of 'bands', with each band containingDNA molecules of a particular size.

The US purchases more products from other countries such as China, however those countries doesn't purchase products from the US.

 Other countries have an excess supply of US dollars that they invest in US  like real estate. That provides those countries the ability to influence the US economy by pulling out their investments. US stock markets allow people to invest in financial products around the world. Stock markets in other countries allow foreigners to invest in the United States. 

Explanation:

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