Because hydrogen bonds hold the two strands of a DNA molecule together, the strands can be separated without breaking any covalent bonds. Every unique DNA molecule "melts" at a different temperature
In this context, Tm(melting temperature) is the point at which two strands separate, or become denatured. Order the DNA sequences listed below according to relative melting temperatures (from lowest Tm to highest Tm). Assume that they all begin as stable double-stranded DNA molecules. Explain your answer.
A. GGCGCACC
B. TATTGTCT
C. GACTCCTG
D. CTAACTGG
The order in which the DNA molecules would denature as the temperature increases is:
1—B; 2—D; 3—C;4—A
All the DNA molecules are the same length, so only the A + T and G + C content determines their relative Tm. Molecules with higher G + C content will be more stable than molecules with a high A + T content. This is because there are three hydrogen bonds between each G-C base pair but only two between each A-T base pair. More energy (heat) is required to disrupt a larger number of hydrogen bonds.
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Fill in the blank(s) with the appropriate word(s).
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