All introns contain a conserved A residue within the intron sequence, usually lo

Question

All introns contain a conserved A residue within the intron sequence, usually located about two-thirds of the distance between the 5 and 3 ends of the intron. During the first step in RNA splicing
A.the intron will be cleaved just before this A residue, triggering exonucleases that degrade the intron from the cleaved ends
B.the 2-position of this A residue will be covalently linked to the 5-end of the intron, forming a lariat
C.the 5-position of this A residue will be covalently linked to the 5-end of the intron, forming a lariat
D.the 3-position of this A residue will be covalently linked to the 5-end of the intron, forming a lariat
E.the 2-position of this A residue will be covalently linked to a conserved U residue found at the 3-end of the intron sequence, forming a lariat

A monocistronic mRNA encodes one protein, while a polycistronic mRNA encodes more than one protein. Which is true?
A. all eukaryotic mRNAs are monocistronic, including those produced by alternative processing
B.most eukaryotic mRNAs are polycistronic, but may be converted to monocistronic mRNAs by alternative processing
C. polycistronic eukaryotic mRNAs are produced by combining exons from different primary transcripts during alternative processing to produce new forms of a protein
D. most eukaryotic mRNAs are polycistronic, including those produced by alternative processing
Eall eukaryotic mRNAs are monocistronic, except for the polycistronic mRNAs produced by alternative processing

In the laboratory, when chromatin is treated with a small amount of nuclease for a short time
A.the proteins in the nucleosomes will dissociate from each other
B.the DNA wrapped around the nucleosome core particles will be preferentially degraded
C.all of the chromatin DNA will be degraded at an equal rate
D.there will be no effect on the chromatin structure
E.the linker DNA between the nucleosome core particles will be preferentially degraded

The form of RNA polymerase that transcribes protein-coding genes in eukaryotic cells
A.requires a set of general transcription factors in order to bind at a promoter
B.requires factor in order to bind at a promoter
C.binds a promoter sequence and carries out transcription without the assistance of other proteins
D.requires only the TATA-binding protein in order to bind at a promoter
E.binds a promoter sequence, and then recruits a set of general transcription factors in order to form an initiation complex

Question 6 of 6

D.binds the sequence AAUAAA near the 3-end of a pre-mRNA molecule

Protein synthesis is a highly accurate process, achieving 99.99% accuracy during translation. Which of the following steps is a major point at which the molecules are checked for accuracy? A.just after the aminoacyl-tRNA binds in the A site, during codon-anticodon basepairing B.just before the “empty” tRNA leaves the E site; the A site is not opened for the arriving aminoacyl-tRNA unless it is the correct one C.just after the small subunit positions the next codon in the A site D.just after the new peptide bond is formed in the peptidyl transferase reaction E.just after the large subunit translocates to shift the positions of the tRNA molecules Reset Selection

Question 6 of 6

2.5 Points Poly-A polymerase (PAP) A.catalyzes the addition of A residues to the new 3-end of a pre-mRNA molecule after cleavage B.cleaves a pre-mRNA molecule just downstream of the AAUAAA sequence, creating a new 3-end C.remains bound to the poly-A tail of a mRNA to stabilize and escort the mRNA through the nuclear pores

D.binds the sequence AAUAAA near the 3-end of a pre-mRNA molecule

Explanation / Answer

1. 2'-OH of A residue will be covalently linked to the 5' end of the intron, forming a lariat

2. (A) All eukaryotic mRNAs are monocistronic, including those produced by alternative processing

3. (E) The linker DNA between the nucleosome core particles will be preferentially degraded, it the DNA accesible to the enzymes

4. (A) Requires a set of general transcription factors in order to bind at promoter

5. (A) just after the aminoacyl-tRNA binds in the A site, during codon-anticodon basepairing

6. (A) catalyzed the addition of A residues to the 3'-end of a pre-mRNA molecule after cleavage

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