Self Quiz Chapter 8 Transcription.doc

1. What are the functions of the four main types of RNA? HTMLCONTROL Forms.HTML:TextArea.1 Answer: (from Different Genes for Different RNAs) mRNA - Messenger RNA: Encodes the amino acid sequence of a polypeptide. tRNA - Transfer RNA: Brings amino acids to ribosomes during translation. rRNA - Ribosomal RNA: With ribosomal proteins, makes up the ribosomes, the organelles that translate the mRNA. snRNA - Small nuclear RNA: With proteins, forms complexes used in RNA processing in eukaryotes. (Not found in prokaryotes.) 2. Describe the differences between DNA and RNA. HTMLCONTROL Forms.HTML:TextArea.1 Answer: DNA contains deoxyribose and thymine, while RNA contains ribose and uracil. DNA is frequently double-stranded, while RNA is usually single-stranded. 3. Which two statements below are correct? HTMLCONTROL Forms.HTML:Checkbox.1 a. During transcription, the template strand is read in a 3'-to-5' direction. HTMLCONTROL Forms.HTML:Checkbox.1 b. During transcription, the template strand is read in a 5'-to-3' direction. HTMLCONTROL Forms.HTML:Checkbox.1 c. During transcription, an RNA is transcribed in the 3'-to-5' direction. HTMLCONTROL Forms.HTML:Checkbox.1 d. During transcription, an RNA is transcribed in the 5'-to-3' direction. Sorry, the correct answers are A and D. 4. Which three statements below are correct? HTMLCONTROL Forms.HTML:Checkbox.1 a. Both prokaryotic and eukaryotic mRNAs have a 5' cap. HTMLCONTROL Forms.HTML:Checkbox.1 b. Only prokaryotic mRNAs are polyadenylated at the 3' end. HTMLCONTROL Forms.HTML:Checkbox.1 c. In prokaryotes, transcription is coupled to translation. HTMLCONTROL Forms.HTML:Checkbox.1 d. In eukaryotes, RNA splicing occurs after the mRNA is transported into the cytoplasm. HTMLCONTROL Forms.HTML:Checkbox.1 e. RNA splicing requires the formation of a spliceosome. HTMLCONTROL Forms.HTML:Checkbox.1 f. Both prokaryotic and eukaryotic mRNAs are synthesized by RNA polymerase. Sorry, the correct answers are C, E, and F. 5. Compare and contrast the structures of prokaryotic and eukaryotic mRNAs. HTMLCONTROL Forms.HTML:TextArea.1 Answer: Prokaryotic mRNAs are not processed; that is, the transcript is the actual molecule that is translated, so the prokaryotic mRNA is colinear with the gene that encoded it. Prokaryotic mRNAs do not have 5' caps or 3' poly(A) tails. Eukaryotic mRNAs have introns removed by RNA splicing before they are transported to the cytoplasm, where they are translated. Eukaryotic mRNAs have 5' caps and a 3' poly(A) tail. 6. What is the function of the promoter? HTMLCONTROL Forms.HTML:TextArea.1 Answer: The promoter is the site where the transcription machinery binds for the initiation of transcription. The two DNA strands are separated in that region, and the RNA polymerase then begins the transcription process. 7. What effect would a mutation in an intron section of a gene have on the expression of the gene? Explain. HTMLCONTROL Forms.HTML:TextArea.1 Answer: In general, a mutation in an intron would have no effect on gene expression because introns are cut out of the mRNA transcript before translation.