Molecular Cell Biology - Problem Drill 08: Transcription, Translation and the Genetic Code

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1 Molecular Cell Biology - Problem Drill 08: Transcription, Translation and the Genetic Code Question No. 1 of Which of the following statements about how genes function is correct? Question #1 (A) Genes store the genetic information in the base sequence and require no further modification to be functional in cells. (B) The information on genes is converted into the functional unit through transcription and translation. (C) The information on genes is converted into the functional unit through transcription and DNA replication. (D) Genes function through proteins and lipids. Genes store the genetic information in the base sequence, but normally this is not the functional unit in cells. B. Correct! The information on genes is converted into the functional unit through transcription and translation. The information on genes is converted into the functional unit through transcription and translation. Genes function through proteins and RNAs. Genes store the genetic information in base sequence, but normally is not the functional unit in cells. Genes function through proteins and RNAs. The information on genes is converted into the functional unit through transcription and translation.

2 Question No. 2 of Which of the following statements about the different classes of RNA is correct? Question #2 (A)Transfer RNA serves a messenger between DNA and protein. (B)Ribosomal RNA carries amino acids to ribosomes for protein synthesis. (C)There are four classes of RNA. These include (1) messenger RNA, (2) transfer RNA, (3) ribosomal RNA and (4) small regulatory RNA. (D)There are three classes of RNA. These include (1) messenger RNA, (2) mitochondrial RNA, and (3) ribosomal RNA. Transfer RNA carries amino acids to ribosomes for protein synthesis. Ribosomal RNA is a structural component for ribosome. C. Correct! There are four classes of RNA. These include (1) messenger RNA, (2) transfer RNA, (3) ribosomal RNA and (4) small regulatory RNA. There are four classes of RNA. These include (1) messenger RNA, (2) transfer RNA, (3) ribosomal RNA and (4) small regulatory RNA. There are four classes of RNA. These include mrna, messenger RNA, which serves a messenger between DNA and protein; trna, transfer RNA, which carries amino acids to ribosomes for protein synthesis; rrna, ribosome RNA, which is a structure component for ribosome, and small RNA which includes snrna, mirna and scrna, they serve as regulatory and/or construction components.

3 Question No. 3 of Which of the following statements about the key players in transcription is correct? Question #3 (A) Messenger RNA is made from a RNA template via transcription. (B) Messenger RNA is made from a DNA template via translation. (C) The transcription process requires: DNA template, RNA polymerase complex, nucleotides ATP, UTP, CTP and GTP. (D) The transcription process requires: DNA template, DNA polymerase complex, nucleotides ATP, TTP, CTP and GTP. Messenger RNA is made from a DNA template via transcription. Messenger RNA is made from a DNA template via transcription. C. Correct! The transcription process requires: DNA template, RNA polymerase complex, nucleotides ATP, UTP, CTP and GTP. The transcription process requires: DNA template, RNA polymerase complex, nucleotides ATP, UTP, CTP and GTP. mrna, i.e., messenger RNA, is made from DNA template via transcription and then directs the protein synthesis. The transcription process requires: DNA template, RNA polymerase complex, nucleotides ATP, UTP, CTP and GTP.

4 Question No. 4 of Which of the following statements about the transcription process is correct? Question #4 (A) Transcription involves three steps: Initiation, Elongation and Termination. (B) During Termination RNA polymerase catalyzes the formation of the RNA while the DNA template is unwound and rewound. (C) During Initiation the DNA polymerase complex assembles at promoter and initiates transcription. (D) During Initiation the RNA polymerase complex assembles at the stop codon and initiates transcription. A. Correct! Transcription involves three steps: Initiation, Elongation and Termination. During Elongation RNA polymerase catalyzes the elongation of the RNA while the DNA template is unwound and rewound. During Initiation the RNA polymerase complex assembles at promoter and initiates transcription. During Initiation the RNA polymerase complex assembles at promoter and initiates transcription. The transcription process can be viewed as three steps: Initiation: RNA polymerase complex assembles at promoter and initiates transcription. Elongation: RNA polymerase catalyzes the elongation of the RNA while the DNA template is unwound and rewound. Termination: transcription complex responds to specific termination signals and disassembles.

5 Question No. 5 of Which of the following statements about promoters is correct? Question #5 (A) A promoter is the region of DNA that signals termination of the translational process. (B) For prokaryotic each gene has its own promoter called an operon. (C) For prokaryotics several genes can be co-transcribed from a single promoter, this is called an operon. (D) For eukaryotes each gene has 3 or more promoters. A promoter is the region of DNA that serves as a site of transcription initiation. For prokaryotics several genes can be co-transcribed from a single promoter, this is called an operon. C. Correct! For prokaryotics several genes can be co-transcribed from a single promoter, this is called an operon. For eukaryotes each gene has 1 or more promoters. Promoter is the region of DNA that serve as sites of transcription initiation, normally located at the 5 end of a gene. For prokaryotics several genes can be cotranscribed from a single promoter, this is called an operon. For eukaryotes: each gene has a promoter, some have multiple promoters. Promoters play critical roles in gene regulation.

6 Question No. 6 of Which of the following statements about heterogeneous nuclear RNA (hnrna) processing is correct? Question #6 (A) During 5 capping a polya chain is added. (B) During 5 capping methyl guanitide is added to the 3 end of the RNA molecule. (C) hnrna processing involves: Splicing, 5 capping and 3 polyadenylation. (D) hnrna processing involves: Splicing, 3 capping and 5 polyadenylation. During 5 capping methyl guanitide is added to the 5 end of the RNA molecule. During 5 capping methyl guanitide is added to the 5 end of the RNA molecule. C. Correct! hnrna processing involves: Splicing, 5 capping and 3 polyadenylation. hnrna processing involves: Splicing, 5 capping and 3 polyadenylation. 5 capping is the process to add a m7guaninotide to the 5 end of mrna, this requires a special enzyme using a special 5-5 link, the function of 5 capping is to protect mrna molecule from 5 exonucleases. The 5 cap is also the site of ribosome attachment during protein synthesis.

7 Question No. 7 of Which of the following statements about RNA splicing is correct? Question #7 (A) The process involves the removal of exon sequences from hnrna. (B) The process involves the removal of intron sequences from hnrna. (C) After the process is completed the intron and exon segments form 2 functional RNA molecules. (D) After the process is completed the intron segments are used to form the ribosomal portion of the translation complex. The process involves the removal of intron sequences from hnrna. B. Correct! The process involves the removal of intron sequences from hnrna. After the process is completed the intron are removed and the exon segments form the functional RNA molecule. After the process is completed the intron are removed and the exon segments form the functional RNA molecule. Splicing is the process to remove the intron sequence from hnrna, the splicing sites are conserved at intron and exon boundary, the process requires a protein/snrna complex called spliceosome. During the splicing, the intron RNA loop out and the spliceosome cuts off the looped out sequence precisely.

8 Question No. 8 of Which of the following statements about the genetic code is correct? Question #8 (A) mrna is read in a sequential manner starting from a fixed point (initiation codon, AUG) and stops at stop codons. (B) mrna is read in a sequential manner starting from a fixed point (intron) and stops at stop codons. (C) Every two bases on mrna determine one amino acid. (D) Every three bases on mrna determine one two amino acids. A. Correct! mrna is read in a sequential manner starting from a fixed point (initiation codon, AUG) and stops at stop codons. mrna is read in a sequential manner starting from a fixed point (initiation codon, AUG) and stops at stop codons. Every three bases on mrna determine one amino acid (triplet code). Every three bases on mrna determine one amino acid (triplet code). In general, the genetic code is the key of how mrna is translated into proteins. During translation, mrna is read in a sequential manner starting from a fixed point (initiation codon, AUG) and stop at stop codons. Every three bases on mrna determine one amino acid (triplet code). Each of 64 combinations (43) of triplet bases encodes an amino acid or a stop codon. One amino acid may be encoded by multiple codons (degeneration, 64 codons vs. 20 amino acids).

9 Question No. 9 of Which of the following statements trna charging during protein translation is correct? Question #9 (A) Each type of trna molecule can be attached to only one type of amino acid. (B) Each type of trna molecule can be attached to more than one type of amino acid. (C) Multiple types of trna bearing different anticodons may carry more than one amino acid at a time (degenerate). (D) Charging is catalyzed by amino-acyl-tdna synthase. A. Correct! Each type of trna molecule can be attached to only one type of amino acid. Each type of trna molecule can be attached to only one type of amino acid. Multiple types of trna bearing different anticodons may carry the same amino acid codon degenerate. Charging is catalyzed by amino-acyl-trna synthase. The first step of protein synthesis is to attach the amino acids to trna, a process called trna charging. Each type of trna molecule can be attached to only one type of amino acid. Multiple types of trna bearing different anticodons may carry the same amino acid codon degenerate. Charging is catalyzed by amino-acyl-trna synthase.

10 Question No. 10 of Which of the following statements about protein translation is correct? Question #10 (A) The peptide occupies the P site in ribosome, the trna brings in next amino acid according to anti-codon base-pairing with mrna, the amino-acid then occupies the A site. (B) The peptide occupies the A site in ribosome, the trna brings in next amino acid according to anti-codon base-pairing with mrna, the amino-acid then occupies the P site. (C) Peptide bond formation involves the formation of a peptide bond between the new amino acid and the trna in the A site. (D) Peptide bond formation involves the formation of a peptide bond between the new amino acid and the trna in the P site. The peptide occupies the P site in ribosome, the trna brings in next amino acid according to anti-codon base-pairing with mrna, the amino-acid then occupies the A site. B. Correct! The peptide occupies the P site in ribosome, the trna brings in next amino acid according to anti-codon base-pairing with mrna, the amino-acid then occupies the A site. Peptide bond formation involves the formation of a peptide bond between the new amino acid and the growing polypeptide chain. Peptide bond formation involves the formation of a peptide bond between the new amino acid and the growing polypeptide chain. The elongation process is assisted by various elongation factors. Decoding and addition of each amino acid to the nascent polypeptide chain involves a three-step minicycle: 1. codon recognition: an incoming aminoacyl-trna binds to codon at A-site. 2. peptide bond formation: peptide bond is formed between new amino acid and growing polypeptide chain. 3. Translocation; trna that was in P site is released. trna in the A site is translocated to the P site. In the process, ribosome advances by one codon.