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. write out the order of 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.
a. ctaactgg
b. tattgtct
c. gactcctg
d. ggcgcacc

The answer to your question is: Order from lowest to highest = B, A, C, D

Explanation:

Just remember that there are two strands of DNA and bases attached specifically to a base.

Adenine attach to thymine

Guanine attach to cytosine,

Also is important to know that Adenine and thymine share 2 hydrogen bonds and Guanine and cytosine share 3 hydrogen bonds, then the higher the number of bonds, the higher the melting point.

A.                                               CTAACTGG  

complementary strand           GATTGACC    

number of bonds                      3,2,2,2,3,2,3,3    Total = 20

B.                                               TATTGTCT

complementary strand           ATAACAGA

number of bonds                     2,2,2,2,3,2,3,2     Total  = 18

C.                                              GACTCCTG

complementary strand          CTGAGGAC

number of bonds                     3,2,3,2,3,3,2,3     Total = 21

D.                                              GGCGCACC

complementary strand          CCGCGTGG

number of bonds                    3,3,3,3,3,2,3,3      Total = 23

Order  B, A, C, D