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What is the difference between genomic DNA, mRNA, and cDNA?

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What is the difference between genomic DNA, mRNA, and cDNA?

Postby Newbie » Wed May 03, 2006 7:34 pm

Hi everyone,

I was wondering what is the difference between genomic DNA and mRNA and cDNA? Genomic DNA contains both genes and non-coding sequences right but doesn't that go for mRNA as well (intron: non-coding, exon: coding)...and cDNA is translated from the mRNA without the non-coding regions? Could someone clarify pretty please?
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Postby canalon » Wed May 03, 2006 8:12 pm

genomic DNA: the natural genetic material
mRNA: the product of transcription, go through some modifications before being translated
cDNA: product of reverse transcription of the mRNA (which has usually already gione through all the modification).

You shoud look up DNA transcription and ReverseTranscription for more details.
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Postby Newbie » Wed May 03, 2006 9:42 pm

Yep...I did thanks. I was just trying to figure out for designing primers if I need to use the cDNA or genomic DNA sequence.
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Postby canalon » Wed May 03, 2006 11:26 pm

depends on what you are looking for:
- Presence of the gene in the genome: gDNA
- Expression of the gene, with RT PCR: mRNA/cDNA
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Postby Newbie » Thu May 04, 2006 6:06 pm

hi Canalon,

Thank you for your patience in answering my questions. I am using QPCR with SYBR method to check for gene expression levels so I assume that I need to take the mRNA/cDNA sequence. However, I tried to use this the PrimerBank website which automatically generates appropriate primer pairs for you and typed in the gene accession number for my gene and I found that the primer pairs that were given actually correspond to the exons on the genomic DNA sequence hence my confusion as to which sequence I am actually supposed to look at. And another thing, I read that it is a good idea to pick primers that span exon borders, is that for both forward and reverse primers...because I think only one of my primers span the border...
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