Biochemistry MCQ Nucleic Acids

1. DNA does not contain
(A) Thymine
(B) Adenine
(C) Uracil
(D) Deoxyribose
ANS – C

2. The sugar moiety present in DNA is
(A) Deoxyribose
(B) Ribose
(C) Lyxose
(D) Ribulose
ANS – A

3. In purine nucleus nitrogen atom at 1 position is derived from
(A) Aspartate
(B) Glutamate
(C) Glycine
(D) Alanine
ANS – A

4. In purine biosynthesis ring closure in the molecule formyl glycinamide ribosyl-5phosphate requires the co-factors:
(A) ADP
(B) NAD
(C) FAD
(D) ATP and Mg++
ANS – D

5. The degradation of RNA by pancreatic ribonuclease produces
(A) Nucleoside 2-Phosphates
(B) Nucleoside 5′-phosphates
(C) Oligonucleosides
(D) Nucleoside 3′-phosphate and oligonucleotide
ANS – D

6. Intestinal nucleosidases act on nucleosides and produce
(A) Purine base only
(B) Phosphate only
(C) Sugar only
(D) Purine or pyrimidine bases and sugars
ANS – D

7. Phosphorylation of adenosine to AMP is catalyzed by
(A) Adenosine kinase
(B) Deoxycytidine kinase
(C) Adenylosuccinase
(D) Adenylosuccinate synthetase
ANS – A

8. Pyrimidine biosynthesis begins with the formation from glutamine, ATP and CO2, of
(A) Carbamoyl aspartate
(B) Orotate
(C) Carbamoyl phosphate
(D) Dihydroorotate
ANS – C

9. The two nitrogen of the pyrimidine ring are contributed by
(A) Ammonia and glycine
(B) Asparate and carbamoyl phosphate
(C) Glutamine and ammonia
(D) Aspartate and ammonia
ANS – B

10. In humans end product of purine catabolism is
(A) Uric acid
(B) Urea
(C) Allantoin
(D) Xanthine
ANS – A

11. A substrate for enzymes of pyrimidine nucleotide biosynthesis is
(A) Allopurinol
(B) Tetracylin
(C) Chloramphenicol
(D) Puromycin
ANS – A

12. Gout is a metabolic disorder of catabolism of
(A) Pyrimidine
(B) Purine
(C) Alanine
(D) Phenylalanine
ANS – B

12. Gout is characterized by increased plasma levels of
(A) Urea
(B) Uric acid
(C) Creatine
(D) Creatinine
ANS – B

13. The eukaryotic nuclear chromosomal DNA
(A) Is a linear and unbranched molecule
(B) Is not associated with a specific membranous organelle
(C) Is not replicated semiconservatively
(D) Is about of the same size as each prokaryotic chromoses
ANS – A

14. Initiation of protein synthesis begins with binding of
(A) 40S ribosomal unit on mRNA
(B) 60S ribosomal unit
(C) Charging of tRNA with specific amino acid
(D) Attachment of aminoacyl tRNA on mRNA
ANS – A

15. Initiation of protein synthesis requires
(A) ATP
(B) AMP
(C) GDP
(D) GTP
ANS – D

16. In eukaryotic cells
(A) Formylated tRNA is important for initiation of translation
(B) Cyclohexamide blocks elongation during translation
(C) Cytosolic ribosomes are smaller than those found in prokaryotes
(D) Erythromycin inhibits elongation during translatio
ANS – B

17. Tetracylin prevents synthesis of polypeptide by
(A) Blocking mRNA formation from DNA
(B) Releasing peptides from mRNA-tRNA complex
(C) Competing with mRNA for ribosomal binding sites
(D) Preventing binding of aminoacyl tRNA
ANS – D

18. Erythromycin acts on ribosomes and inhibit
(A) Formation of initiation complex
(B) Binding of aminoacyl tRNA
(C) Peptidyl transferase activity
(D) Translocation
ANS -D

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