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-   -   Why cDNA and not DNA? (http://www.molecularstation.com/forum/cdna-forum/3602-why-cdna-not-dna.html)

jiji324 07-20-2008 05:23 AM

Why cDNA and not DNA?
 
Hello all,
Why is do scientists use cDNA (complementary DNA) in plasmids used for cloning DNA instead of "regular" DNA?

What it the difference between these two: DNA and cDNA?
:badgoalie:
thank you

gandalfthegrey 07-20-2008 05:26 AM

Re: Why cDNA and not DNA?
 
Hi,
cDNA is short for complementary DNA. It is DNA which has been reverse transcribed from mature mRNA. DNA is much more stable than RNA, so cDNA is used to make a copy of the DNA (cDNA also stands for copy DNA go figure :cussing:)

Okay, eukaryote DNA (we're eukaryotes, by the way) has segments in it that don't really code for anything useful. These segments are called introns. The segments between introns that DO contain useful code are called exons. Normally, when DNA is transcribed to make mRNA, the mRNA then goes through processing to splice out the introns and glue the exons together. The result is a piece of mRNA that is ready for translation in the ribosomes.

Prokaryotes (bacteria) don't have introns, and they don't have any mechanisms for removing introns from eukaryotic DNA. Hence, if you want to insert a human gene into a bacterium, you have to remove the introns yourself. But how do you do that You take a segment of mRNA that has already been processed, and reverse transcribe it into cDNA. The cDNA lacks the introns that were part of the original DNA and is ready for insertion into a plasmid.

hope this helps you!

saurabhgene 09-27-2009 01:16 PM

Re: Why cDNA and not DNA?
 
Nice answer

veniesh 09-27-2009 05:52 PM

Re: Why cDNA and not DNA?
 
i think this answer not complete because question is "What it the difference between these two: DNA and cDNA?" but gandalfthegrey give answer is different between cDNA and RNA.

jiji324 also ask "Why is do scientists use cDNA (complementary DNA) in plasmids used for cloning DNA instead of "regular" DNA ? why scientists not used DNA?" but gandalfthegrey give answer is DNA is much more stable than RNA...

so i done this question is correct or the answer is correct? the answer not related to this question....!!

iyos 09-28-2009 08:06 AM

Re: Why cDNA and not DNA?
 
why cDNA and not DNA???

cDNA = complementary DNA and is double stranded DNA which synthesized from mature mRNA.

In gene cloning, a gene is transferred from one cell into another cell, then a new genetic material being expressed in the recipient cell as a protein.

'regular' DNA = contains the entire gene including exons (coding segments) and introns (non coding segment)

The introns do not code for protein, and may interrupt the coding sequence of protein in the cloning process. That's why cDNA is trasferred to the recipient cell rather that the whole DNA.
Although cDNA referred to partial sequences, but a significant expression can be obtained.

-please correct me if wrong- tq

veniesh 09-28-2009 04:45 PM

Re: Why cDNA and not DNA?
 
cDNA is reverse transcribed RNA, thus it represent the transcript of the genomic DNA.
There are several differences between transcript and genomic DNA
1. cDNA doesn't contain introns.
2. cDNAs are much shorter, as introns can span thousands of pase pairs, and therefore easily cloned and worked with.


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