Following statements are regarding to enzymatic processing of benzo(a)pyrene to a more potent mutagen and carcinogen.

A. Liver enzymes, particularly P-450 enzymes, modify benzo(a)pyrene in a series of reactions, producing 7,8-diol-9,10-epoxide, a highly potent mutagenic species that reacts with DNA primarily at the N2 atom of a guanine base.

B. The adduct, (+)-trans-anti-B(a)P-N2-dG, causes polymerase to insert an A rather than a C opposite the modified G base. Next time the DNA is replicated, a T will be inserted opposite the A, and the mutation will be complete.

C. Potent mutagen majorly causes conversion of guanine (G) to thymine (T) bases, a transition mutation.

D. When this potent mutagen applied to cultured bronchial epithelial cells, activated benzo(a)pyrene induces many mutations, including activating mutations at codons 175, 248, and 273 of the p53 gene.

Which of the following statements are correct?

#Question id: 4273

#Unit 3. Fundamental Processes

80S initiation complex includes

#Question id: 4274

#Unit 3. Fundamental Processes

One mechanism that contributes to the fidelity of codon recognition involves the 16S rRNA other than initiation. Which of the following statements are correct in this phenomenon?

A. Codon recognition involves two adjacent uracil residues in the 16S rRNA component

B. The adjacent residues in the 16S rRNA do not discriminate between G:C or A:U base pairs and recognize either as correct

C. Even a single mismatch in the codon–anticodon base pairing alters the position of EF-Tu, reducing its ability to interact with the factor-binding center 16s rRNA, leads to a dramatic reduction in EF-Tu GTPase activity

D. Pyrophasphatic editing is key mechanism to ensure fidelity

#Question id: 4275

#Unit 3. Fundamental Processes

CCA-adding enzymes add a specific sequence without a template because

#Question id: 4276

#Unit 3. Fundamental Processes

Which of the following post-translational modifications of proteins occur(s) in the lumen of the endoplasmic reticulum?

a. glycosylation                       b. formation of disulfide bonds

c. conformational folding and formation of quaternary structure

d. proteolytic cleavage                        e. aldol condensation of sugars

#Question id: 4277

#Unit 3. Fundamental Processes

N-linked oligosaccharides in glycoproteins

#Question id: 4278

#Unit 3. Fundamental Processes

N-terminal sequences usually function as targeting signals for protein transport into

a. the nucleus.             b. peroxisomes.                       c. chloroplasts.

d. the rough endoplasmic reticulum.   e. mitochondria.