The 3' end of DNA
A) has a hydroxyl group attached to the number 3 carbon of deoxyribose.
B) attaches to the 3' phosphate group of the incoming nucleotide.
C) always has thymine and uracil attached to it.
D) usually has guanine and guanine attached to it.
E) has a hydroxyl group attached to the number 3 carbon of ribose.

Question

Quizplus · Accepted Answer

The 3' end of DNA has a hydroxyl group (-OH) attached to the number 3 carbon of deoxyribose. This hydroxyl group is important for the formation of phosphodiester bonds between nucleotides during DNA synthesis.

Answer: B
 The 3' end of DNA attaches to the 3' phosphate group of the incoming nucleotide during DNA synthesis through the formation of a phosphodiester bond. This reaction involves the removal of a pyrophosphate molecule from the incoming nucleotide, and the formation of a covalent bond between the 3' hydroxyl group of the previous nucleotide and the 5' phosphate group of the new nucleotide.

Answer: C, D, and E are all incorrect.
 The nucleotides attached to the 3' end of DNA can vary and are not limited to thymine, uracil, guanine or cytosine. Also, the 3' end of DNA always has a deoxyribose sugar attached to it, so it cannot have the hydroxyl group attached to a ribose sugar (-OH instead of -H at the 2' carbon).

The 3' End of DNA