Test 2 Question 2 Help

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Jasmine 2C
Posts: 109
Joined: Wed Sep 18, 2019 12:18 am

Test 2 Question 2 Help

Postby Jasmine 2C » Fri Dec 06, 2019 3:53 pm

Q2A: "Hydrogen bonding is important for nucleic acids. Draw how two separate nucleic acids below (guanine (G) and cytosine (C)) will interact via H-bonding to form a GC pair."
- can someone explain where the H-bonds are and how they're formed?

Q2.B: "There are two different base pairs in a DNA molecule, a GC pair as described in (a) and a adenine-thymine (AT) pair. Which pair has a higher melting point in a DNA molecule: a GC pair, or an AT pair? Why?
- for this question, are we supposed to just memorize how guanine pairs with cytosine and how adenine pairs with thymine?

John Liang 2I
Posts: 56
Joined: Fri Aug 30, 2019 12:18 am

Re: Test 2 Question 2 Help

Postby John Liang 2I » Fri Dec 06, 2019 3:57 pm

Jasmine 3L wrote: Q2A: "Hydrogen bonding is important for nucleic acids. Draw how two separate nucleic acids below (guanine (G) and cytosine (C)) will interact via H-bonding to form a GC pair."
- can someone explain where the H-bonds are and how they're formed?

Q2.B: "There are two different base pairs in a DNA molecule, a GC pair as described in (a) and a adenine-thymine (AT) pair. Which pair has a higher melting point in a DNA molecule: a GC pair, or an AT pair? Why?
- for this question, are we supposed to just memorize how guanine pairs with cytosine and how adenine pairs with thymine?


I can answer 2B: The GC pair has 3 H bonds, while the AT pair has 2 H bonds. More H Bonds equals stronger IMF. Therefore, the GC pair is higher has a higher melting point.

Junxi Feng 3B
Posts: 52
Joined: Sat Sep 14, 2019 12:17 am

Re: Test 2 Question 2 Help

Postby Junxi Feng 3B » Fri Dec 06, 2019 4:04 pm

For part A, the hydrogen bonds form like bridges across the nucleic acid between the O, N, H atoms.
For part B, the hydrogen bond between AT is 2, so it is weaker than the hydrogen bond between CG, which is 3.


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