DNA gyrase produces, then seals, double-strandedbreaks.

SI nuclease is used to cleave hairpin loop and results in double stranded cDNA (Fig.

They are up to 200 kb long, double-stranded,circular DNA molecules.

The reverse transcriptase uses the free end and synthesizes a single stranded cDNA in the presence of dCTP, dGTP, dATP and dTTP, and results in mRNA-cDNA hybrid.

The single stranded cDNA complementary to mRNA is tailed with oligo-dC tail.

Is cDNA a single or double stranded ? - Molecular Cloning

you need to differenciate 2 things :

cDNA in general is the DNA molecule corresponding roughly to the mRNA seuqence. So It's a double stranded molecule included in plasmid for expression in most cases.

RT PCR : the mRNA molecule is reverse transcribed in cDNA single strand. After this point RNase eliminates the mRNA molecule and you get a single stranded cDNA molecule. As the next step is quite classical PCR, a single strand is ok for the exp (and the first step, which corresponds to sysnthesis of the corrseponding second strand of a DNA molecule restores the real cDNA molecule.

To be right, cDNA is a double stranded molecule, but for convenience, cDNA is also used for designing the reverse transcribed molecule of the RTPCR. It should be named as half cDNA or single strand cDNA.
cDNA is a shorting name.

From this point it replaces the 'nicked' strand by itsexonuclease activity while polymerizing the DNA strand using the nondigestedstrand as template.

DNA probes with conjugated MGB groups form extremely stable duplexes with single-stranded DNA targets, allowing shorter probes to be used for hybridization based assays. In comparison with unmodified DNA, MGB probes have higher melting temperature (Tm) and increased specificity, especially when a mismatch is in the MGB region of the duplex. MGB probes, therefore, can be significantly shorter than traditional probes, providing better sequence discrimination and flexibility to accommodate more targets.

Other differences from DNA are: it containsuracil instead of thymine, it is single-stranded, and its sugar molecule isribose.

involves the synthesis of cDNA, which has to be double stranded ..

So, cDNA is single stranded until a PCR reaction is carried out ? Ok, in this case, how Taq DNA Polymerase generates a second complementary strand from only one ? When the two primers anneal to each side of the same strand, how they can produce the second strand (the new complementary one) ?

Second-Strand cDNA Synthesis Kit - Biocrede Inc.

For most cases, such for RT-PCR, 3' or 5' RACE, we just use single stranded cDNA (the first strand cDNA), while in case of preparing the cDNA for library construction, or RDA/SSH analysis which might need additional second strand synthesis step for generate double strand cDNA.

SuperScript Double-Stranded cDNA Synthesis Kit …

In some experiments such as microarray, double-stranded cDNA is required and can be produced by another round of DNA synthesis following the first strand synthesis.

Second-Strand cDNA Synthesis Kit-dNTP based


I posted my question elsewhere but hadn't answer, I'd like to post it here and, sorry it seems stupid question, because I'm really confused !

I read in somwhere a thing which perplexed me about cDNA. I'd like to know if cDNA is a double stranded or a single stranded ?

I know that cDNA is the copy of mRNA by reverse transcriptase so, theorically, it would be a single stranded , right or I'm mistake ?

Thanks for your feedback

Double strand cdna synthesis invitrogen

The synthesis of DNA from an RNA template, via reverse transcription, produces complementary DNA (cDNA). Reverse transcriptases (RTs) use an RNA template and a short primer complementary to the 3' end of the RNA to direct the synthesis of the first strand cDNA, which can be used directly as a template for the Polymerase Chain Reaction (PCR). This combination of reverse transcription and PCR (RT-PCR) allows the detection of low abundance RNAs in a sample, and production of the corresponding cDNA, thereby facilitating the cloning of low copy genes. Alternatively, the first-strand cDNA can be made double-stranded using DNA Polymerase I and DNA Ligase. These reaction products can be used for direct cloning without amplification. In this case, RNase H activity, from either the RT or supplied exogenously, is required.