Question

When heated, the hydrogen bonds between the complementary strands of DNA break and the 2 strands separate in a process called melting. Which of the following pieces of DNA will require maximum temperature for melting?

• A. $3^{\prime }AAGGTATACAAT{5}^{\prime }{5}^{\prime }TTCCATATGTTA{3}^{\prime }$
• B. $3^{\prime }GAGCUAUCCGAG{5}^{\prime }{5}^{\prime }CUCGAUAGGCUC{3}^{\prime }$
• C. $3^{\prime }ACGTCCGCTGCG{5}^{\prime }{5}^{\prime }TGCAGGCGACGC{3}^{\prime }$
• D. $3^{\prime }ATTAGCTAGCAA{5}^{\prime }{5}^{\prime }TAATCGATCGTT{3}^{\prime }$

Answer 1

The correct option is C $3^{\prime }ACGTCCGCTGCG{5}^{\prime }{5}^{\prime }TGCAGGCGACGC{3}^{\prime }$

As we know that, DNA has adenine, thymine, cytosine and guanine as its base pairs where A binds with T with double hydrogen bond while G binds with C with triple hydrogen bond. To separate the two strands of DNA we need maximum temperature to melt the hydrogen bonds and the temperature is increased as the total hydrogen bond number is increased because it is more tough to break the bonds. So, here we see that the third option has the maximum number of hydrogen bonds, that's why it needs maximum temperature for melting.
So, the correct option is option C.