Does the mRNA model more closely resemble the DNA strand from which is was transcribed or the complementary strand that wasn't used? Explain.

Interesting question! You could say it more resembles the complementary strand, with a major difference. When mRNA is formed, DNA first "unzips"; the DNA is a two sided chain of nucleic acids. There are four types of nucleic acids in DNA, arranged in a long chain. Adenine always pairs with thymine, and cytosine with guanine. So when the mRNA forms from one side of the DNA molecule, it essentially looks like the other strand of DNA because the other part of the A/T, or C/G pair will line up with what is on the DNA strand. There is a key difference, though--instead of thymine, mRNA has a different nucleic acid, uracil. So except for the substitution of uracil for thymine on the mRNA molecule, it looks just like the side of the DNA that was not copied.