What are the differences between DNA replication and mRNA transcription?

The major difference between both of these processes is why they are used, DNA replication is used for cell division in the S phase of the cell cycle. mRNA transcription is used in protein synthesis and therefore gene expression. DNA replication produces another copy of DNA, with one strand being from the original molecule and one brand new strand. Whereas mRNA transcription turns a DNA molecule into one strand of DNA. The scales of the two processes are different as DNA replication copies DNA from a whole chromosome however mRNA transcription only uses a short section of the DNA molecule (the gene)as a template. In DNA replication the enzyme used to break the hydrogen bonds between the bases is DNA helicase, alternatively it is RNA helicase in transcription. Also DNA replication uses DNA polymerase and transcription uses RNA polymerase to create the new phosphodiester bonds. In replication all of the molecule unzips however in transcription only the gene region unzips.