It depends on GC content and if GC content is about 50%, than the melting point is around 50C.
Because three hydrogen bonds form between guanine/cytosine base pairs and two hydrogen bonds form between adenine/thymine base pairs, more energy is required to denature the former. DNA with a greater number of guanine/cytosine base pairs denatures at a higher temperature than adenine/thymine base pairs. In fact, there is a linear relationship between the amount of guanine and cytosine in a given DNA molecule, known as the GC content, and the temperature at which the double helix will denature, called the melting point (denoted as tm). (Redirected from DNA melting). Nucleic acid thermodynamics is the study of how temperature affects the nucleic acid structure of double-stranded DNA (dsDNA). The melting temperature (Tm) is defined as the temperature at which half of the DNA strands are in the random coil or single-stranded (ssDNA) state. Tm depends on the length of the DNA molecule and its specific nucleotide sequence. The melting temperature, T m, occurs when half of the double-stranded nucleic acid has dissociated. If no additional nucleic acids are present, then [A], [B], and [AB] will be equal, and equal to half the initial concentration of double-stranded nucleic acid, [AB] initial. The melting temperature, T m, of an oligonucleotide is its most critically important value. The most reliable and accurate determination of melting temperature is determined empirically, however, this is cumbersome and not usually necessary. The melting temperature for the sequence TGCTCA is, 2(1+2) + 4(1+2) = 18°C. The nature of the immobilized target strand provides a net decrease in the T m observed when both target and probe are free in solution. The magnitude of the decrease is approximately 7-8°C. The melting temperature (Tm) is defined as the temperature at which half the DNA strands are in the double-helical state and half are in the random-coil state. The CG content of an oligonucleotide is the most important factor that influences the Tm value.  Melting DNA. Large DNA molecules may melt by segments Since the a:t base pair is held together by only two hydrogen bonds, while the g:c pair has three, you might guess that melting temperature was just a function of percent a:t pairs. Generally DNA rich in a:t does have a low melting temperature.  Posted. The ratio of GC to AT base pairing, an increase in GC base pairs means there are more hydrogen bonds (3 instead of 2 in between A and T) and that will increase the melting point.  Best Answer: Melting point of DNA is related to the GC content of it. Since GC forms three hydrogen bonds, while AT forms two hydrogen bonds, the more GC you have in your DNA the higher the melting point will be. If the GC content is about 50%, the melting point is around 50C. The exact number is hard to calculate and there really isn't a universally accepted way of calculating melting temp base on the sequence. You can monitor DNA melting through UV light. Melting curve analysis is an assessment of the dissociation-characteristics of double-stranded DNA during heating. As the temperature is raised, the double strand begins to dissociate leading to a rise in the absorbance intensity, hyperchromicity. The temperature at which 50% of DNA is denatured is known as the melting point, though it is an inaccurate term as it has very little to do with a traditional melting point. The information gathered can be used to infer the presence and identity of single-nucleotide polymorphisms (SNP).
http://www.biology.arizona.edu/biomath/tutorials/Linear/LinearFunctionApplication/DNAmelt.html https://en.wikipedia.org/wiki/DNA_melting http://www.sigmaaldrich.com/technical-documents/articles/biology/oligos-melting-temp.html http://primerdigital.com/fastpcr/m7.html http://www.scienceisart.com/A_DNA/Melt_2.html http://www.scienceforums.net/topic/28923-melting-point-of-dna/ https://answers.yahoo.com/question/index?qid=20060713114403AAjfpll https://en.wikipedia.org/wiki/Melting_curve_analysis
dna melting temperature