Question

There are two distinct immunodeficiency diseases that lead to the formation of uric acid as the end product. Mutation in genes for adenosine deaminase (ADA) leads to severe combined immunodeficiency (SCID) in which both T-cells and B-cells are affected. Defects in purine nucleoside phosphorylase (PNP) affect only T-cells. These two enzymes are in the pathways for degradation of nucleic acids. Gene therapy has had some success in treating ADA deficiency. In nucleic acid degradation, all of the following are correct except A there are nucleases that are specific for either DNA or RNA. B. nucleotidases convert nucleotides to nucleosides. C. the conversion of a nucleoside to a free base is an example of a hydrolysis. D. because of the presence of deaminases, hypoxanthine rather than adenine is formed. E. both DNA and RNA degradation lead to uric acid.

Short answer

Answer: E. both DNA and RNA degradation lead to uric acid.

Step-by-step solution

Analyze Statement A

Statement A says that there are nucleases specific for either DNA or RNA. This is true, as there are enzymes like DNases that specifically degrade DNA and RNases that specifically degrade RNA. Hence, statement A is correct.

Analyze Statement B

Statement B says that nucleotidases convert nucleotides to nucleosides. This is also true. Nucleotidases hydrolyze the phosphate group from nucleotides, converting them to nucleosides. Hence, statement B is correct.

Analyze Statement C

Statement C says that the conversion of a nucleoside to a free base is an example of hydrolysis. This is true, as nucleosidases are enzymes that catalyze the hydrolysis of nucleosides into free bases and ribose or deoxyribose sugar. Hence, statement C is correct.

Analyze Statement D

Statement D says that due to the presence of deaminases, hypoxanthine rather than adenine is formed. Deaminases are enzymes that remove the amino group from molecules, such as adenosine. Adenosine deaminase converts adenosine to inosine, which then converts to hypoxanthine. Hence, statement D is correct.

Analyze Statement E

Statement E says that both DNA and RNA degradation lead to uric acid. This statement is incorrect. Uric acid is formed as the end product of purine degradation, which includes adenine and guanine bases. However, not all bases in DNA and RNA are purines; there are also pyrimidines like cytosine, thymine, and uracil. Pyrimidine degradation does not lead to uric acid formation. Therefore, statement E is incorrect. The incorrect statement is: E. both DNA and RNA degradation lead to uric acid.