Nucleotide structure question

Question

https://quizlet.com/_69plfz (image is at the top)

What is true of the picture above

1. it is an RNA molecule
2. it is a DNA molecule
3. #1 is a purine
4. #2 is a pyrimidine
5. . the molecules 5' end is the closest to 1
6. if combined into one structure all the circled molecules would constitute a nucleotide

a. 2, 4, and 5 are correct

b. 2, 3, 4, and 6 are correct

c. 2, 3, 4, and 5 are correct

d. 2 and 4 are correct

e. 1,2,3, and 5 are correct

Answer 1

The molecule in question is the DNA, or Deoxyribose Nucleic Acid. This can be determined by examining the 2' carbon of the five-membered sugar, deoxyribose. If this position contained an hydroxy group (^-OH), it would be the sugar ribose found in RNA. However, since it is deoxygenated at this position and only has two hydrogens bonded to the carbon, it is deoxyribose.

The circled molecule is the nucleotide of the DNA. DNA has one of two types of nucleotides: either a single-cyclic pyrimidine or a double-cyclic purine. I differentiate between these two by remembering a pyramid has a single base.

For the numbering of the deoxyribose, 1' begins at the carbon to the right of the oxygen in the ring and ends with the carbon that is not in the ring. Therefore, statement 5 is incorrect: carbon 4 is closest to carbon 1.

Reviewing the answers, no answer is correct. The validity the answer to this problem should be questioned as all answers have 3 and/or 4 being correct when in fact they have mislabeled the pyrimidine and purine. If this was the case, and 1 should refer to a pyrimidine and 2 should refer to a purine, choice "b" would be correct.