Question

1. Given the DNA strand AAACCCGGGTTT, I want you to give me the complimentary mRNA strand. (remember use uracil in place of thymine!!)

Answer 1

UUUGGGCCCAAA would be the complimentary strand

Answer 2

I guess you are asking for the complimentary strand of 3' - AAACCCGGGTTT - 5' am I right? If so...

The complimentary mRNA strand will be 5' - UUUGGGCCCAAA - 3'
A will always pair with T, or U in the case of RNA strands.
C will always pair with G in both DNA and RNA.

The reason for guessing that you were asking for 3' - 5' DNA:
mRNA is synthesised during transcription of a DNA strand, where RNA polymerase (which catalyses the formation of phosphodiester bonds between Ribonucleic Acid (RNA) molecules) reads the DNA strand in the 3' to 5' direction. So, the 5' end of mRNA will first be synthesised, and a 5' guanosine cap will be synthesised in mRNA during post-transcriptional modification. After mRNA strand has been synthesised, a poly-A tail will be added to the 3' end of mRNA during post-transcriptional modification.

Hope this helps! :)