Question

Which of the following statements is true? A. RNA polymerase has a proofreading activity B. Prokaryotic RNA usually undergoes nuclear processing C. Polypeptides are synthesized by addition of amino acids to the amino terminus. D. The 3' end of mRNA corresponds to the carboxyl terminus of the protein. Grade 2. Which of the following A. It may be autocatalytic. B. Spliceosomes are present in organelles and nuclei C. It involves removal of exons is true regarding RNA processing? D. It occurs in prokaryotes. E. None of the above 3. Which of the following features is common to both DNA replication and transcription? A. Nucleotides are added to the 5' end of the newly synthesized strand B. A sugar-phosphate bond is formed between the 3' hydroxyl and the 5 phosphate C. Deoxyribonucleotides are incorporated into the growing sequence. D. Both RNA and DNA polymerases require oligonucleotide priming 4. The site of RNA polymerase binding to the DNA template is called A. Enhancer B. Domain C. Leader sequences D. Carboxyl end E. Promoter 5. A DNA strand consists of any sequence of four kinds of nucleotides. Suppose there were only 16 different amino acids instead of 20. Which of the following statements would be correct descriptions of the minimal number of nucleotides necessary to create a genetic code? A. I B. 2, provided that chain termination does not require a special codon C. 3, provided that chain termination does require a special codon D. 2, no matter how chain termination is accomplished E. Both B and C 6. All of the following may result from promoter mutations, except A. Decreased affinity for RNA polymerase B. Increased affinity for RNA polymerase C. Mutant RNA polymerase D. Unregulated transcription E. A new phenotype 7. In prokaryotes, the strength of the binding of RNA polymerase to different promoters A. Is approximately the same B. Depends on the promoter sequences C. Depends on enhancer sequences D. Depends on promoter-enhancer interaction E. Is different for different types of RNA polymerase 8. Introns within primary eukaryotic transcripts A. Are joined to form mature mRNA B. Are highly conserved in nucleotide sequence C. Often function as exons in other genes D. Vary considerably in size and number among different genes

Answer 1

Ans 1: RNA polymerase has proofreading activity

RNA polymerase is an enzyme that possess the proofreading activity which are mainly of two types: 1. Pyrophosphorolytic editing: It is a type of reaction mechanism where an incorrectly inserted ribonucleotide is removed immediately by reincorporation of the pyrophosphate (PPi) by the enzyme RNA polymerase. 2. Hydrolytic editing: It is a type of reaction mechanism where polymerase enzyme backtracks by one or few nucleotides cleaves the wrongly inserted RNA product and performs subsequent removal of error containing sequences from the nascent mRNA chain. All other options are not appropriate since prokaryotic RNA doesn't undergo nuclear processing such as splicing, It occurs in eukaryotes, Option C is not correct since polypeptides are made by addition of amino acid to the carboxyl group of the previous amino acid which results in the formation of a peptide bond between carboxyl group of one amino acid and amino group of the other. Option D is not correct since 3' end of mRNA doesn't correspond to carboxyl terminus of the protein.