Identify the ODD term in each set and name the CATEGORY to which the remaining three belong:
Adenine, Guanine, Creatinine, Cytosine
Topic: Nitrogenous bases
Answer
Odd one out: CREATININE. Category of the others: NITROGENOUS BASES OF DNA.
Adenine, guanine and cytosine are NITROGENOUS BASES found in DNA (with thymine as the fourth).
CREATININE is a nitrogenous WASTE PRODUCT, formed from the breakdown of creatine phosphate in muscle and excreted by the kidneys in urine. It has nothing to do with the genetic code.
THE TRAP is that all four words sound alike and all contain nitrogen. The distinction is between a component of DNA and a waste product of metabolism.
A doctor measures blood creatinine to judge how well the kidneys are working: if the filtering fails, creatinine accumulates in the blood instead of being excreted.
Note also the pairing among the three correct terms — ADENINE and GUANINE are PURINES (double-ringed), CYTOSINE is a PYRIMIDINE (single-ringed) — but that would split them two-and-one, which is not what the question wants.