AP BIOLOGY

THE MOLECULAR BASIS OF INHERITANCE

STRUCTURE OF NUCLEIC ACIDS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Guanine forms ____ phosphodiester bond(s) with cytosine.
A
One
B
Two
C
Three
D
None, they form hydrogen bonds
Explanation: 

Detailed explanation-1: -Guanine pairs with cytosine with 3 hydrogen bonds. This creates a difference in strength between the two sets of Watson and Crick bases. Guanine and cytosine bonded base pairs are stronger then thymine and adenine bonded base pairs in DNA.

Detailed explanation-2: -The Adenine-Thymine base pair is held together by 2 hydrogen bonds while the Guanine-Cytosine base pair is held together by 3 hydrogen bonds.

Detailed explanation-3: -Guanine pairs with cytosine, and adenine pairs with thymine in DNA. Interstrand hydrogen bonds are responsible for this pairing.

Detailed explanation-4: -Guanine always forms three hydrogen bonds with cytosine.

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