CH 17 MB transcription and translation
Which of the following statements about ribozymes is/are correct?
-Ribozymes are RNA molecules that function as enzymes. -A ribosome can be regarded as one large ribozyme. -In some genes, intron RNA functions as a ribozyme and catalyzes its own excision.
Which of these is currently considered the best definition of a gene?
A gene codes for either a polypeptide or an RNA molecule.
The diagram below shows an mRNA molecule that encodes a protein with 202 amino acids. The start and stop codons are highlighted, and a portion of the nucleotide sequence in the early part of the molecule is shown in detail. At position 35, a single base-pair substitution in the DNA has changed what would have been a uracil (U) in the mRNA to an adenine (A). Based on the genetic code chart above, which of the following would be the result of this single base-pair substitution?
A nonsense mutation resulting in early termination of translation
After transcription begins, several steps must be completed before the fully processed mRNA is ready to be used as a template for protein synthesis on the ribosomes. Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus?
A) A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA. C) Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes. E) A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA.
Which of the following is not true of RNA processing? A) Exons are cut out before mRNA leaves the nucleus. B) Nucleotides may be added at both ends of the RNA. C) Ribozymes may function in RNA splicing. D) RNA splicing can be catalyzed by spliceosomes. E) A primary transcript is often much longer than the final RNA molecule that leaves the nucleus.
A) Exons are cut out before mRNA leaves the nucleus.
Which one of the following is true of tRNAs? A. There are four types of tRNA. B. tRNAs carry special sequences known as codons. C. tRNAs are double-stranded. D. Each tRNA binds a particular codon. E. NONe of the above
E. The correct response is not listed in the choices. The tRNA transfers an amino acid to the growing polypeptide chain. It is a molecule involved in translation of mRNA.
Which of these correctly illustrates the pairing of DNA and RNA nucleotides?
GTTACG CAAUGC
Which of the following molecules are produced by transcription?
Messenger RNA Ribozymes
In the diagram below, the gray unit represents _____.
RNA polymearse
__________________ is the process by which a DNA template is used for the manufacture of several different types of RNA.
Transcription
What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA?
Transcription ( is the process by which a DNA template is used for the manufacture of several different types of RNA.)
Enter the sequence of bases as capital letters with no spaces and no punctuation. Begin with the first base added to the growing RNA strand, and end with the last base added.
UGAGCC
Which of the following clues would tell you if a cell is prokaryotic or eukaryotic?
Whether or not the cell is compartmentalized by internal membranes
What is a ribozyme?
a biological catalyst made of RNA
Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?
a frameshift deletion at the beginning of the gene
The anticodon of a particular tRNA molecule is
complementary to the corresponding mRNA codon
The flow of information in a cell proceeds in what sequence?
from DNA to RNA to protein
After an RNA molecule is transcribed from a eukaryotic gene, what are removed and what are spliced together to produce an mRNA molecule with a continuous coding sequence?
introns ... exons (Introns, intervening sequences, are removed and the exons, expressed sequences, are spliced together.)
RNA processing converts the RNA transcript into _____.
mRNA
RNA _____________ edits the RNA transcript that has been assembled along a DNA template.
processing
The _____________ is the region of DNA at which the process of transcription begins.
promoter
Which of the following terms associated with transcription describe regions of nucleic acid?
promotor, gene, terminator
Which of the following is not true of a codon? A) It consists of three nucleotides. B) It may code for the same amino acid as another codon. C) It never codes for more than one amino acid. D) It extends from one end of a tRNA molecule. E) It is the basic unit of the genetic code.
It extends from one end of a tRNA molecule.
Where does RNA polymerase begin transcribing a gene into mRNA?
It starts after a certain nucleotide sequence called a promoter (In both eukaryotes and prokaryotes, RNA polymerase binds to the gene's promoter and begins transcription at a nucleotide known as the start point, although in eukaryotes the binding of RNA polymerase to the promoter requires transcription factors.)
Place the events in the transcription of a gene in their proper order from left (first event) to right (last event).
1) first transcription event: RNA polymerase binds promoter 2)second transcription event: RNA polymerase transcribes gene 3) third transcription event: RNA polymerase reaches terminator 4) last transcription event: RNA polymerase exits gene, RNA is released (Transcription begins when a molecule of RNA polymerase binds to a promoter. Transcription continues through the gene, producing the RNA. Once RNA polymerase reaches the terminator, the RNA is released, and RNA polymerase falls off the DNA.)
Given a DNA molecule with the sequence of bases 5'-ATTGCA-3', what would be the sequence of the complementary strand? (It will be helpful to draw the DNA molecule when answering the question.)
3'-TAACGT-5'
The direction of synthesis of an RNA transcript is _____.
5' —> 3' (Nucleotides are added to the 3' end of RNA)
Using Figure 17.5 in your textbook, identify a 5' →→ 3' sequence of nucleotides in the DNA template strand for an mRNA coding for the polypeptide sequence Phe-Pro-Lys.
5′-CTTCGGGAA-3′
What is the function of RNA polymerase?
It unwinds the double helix and adds nucleotides to a growing strand of RNA. (RNA polymerase has several functions in transcription, including unwinding the DNA double helix and adding RNA nucleotides.)
Which of the following mutations would be most likely to have a harmful effect on an organism? A) a nucleotide-pair substitution B) a deletion of three nucleotides near the middle of a gene C) a single nucleotide deletion in the middle of an intron D) a single nucleotide deletion near the end of the coding sequence E) a single nucleotide insertion downstream of, and close to, the start of the coding sequence
E) a single nucleotide insertion downstream of, and close to, the start of the coding sequence
What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?
Translation
_______________ is the process by which information encoded in RNA is used to manufacture a polypeptide.
Translation
Polypeptides are assembled from _____.
amino acids (Proteins are composed of amino acid monomers.)
In the diagram below, the two blue strands represent _____.
dna
What name is given to the process in which pre-mRNA is edited into mRNA?
RNA processing
In eukaryotic cells, transcription cannot begin until
several transcription factors have bound to the promoter.
During transcription in eukaryotes, a type of RNA polymerase called RNA polymerase II moves along the template strand of the DNA in the 3'→5' direction. However, for any given gene, either strand of the double-stranded DNA may function as the template strand. For any given gene, what ultimately determines which DNA strand serves as the template strand?
the base sequence of the gene's promoter
A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain
three ... amino acid
In RNA, uracil takes the place of ____________
thymine.
Which of the following molecules is/are produced by translation? Include molecules that are subject to further modification after initial synthesis.
Aminoacyl-tRNA synthetase RNA polymerase (RNA polymerase and aminoacyl-tRNA synthetase, like other proteins, are produced by translation of mRNA, when amino acids such as glycine are linked to form polypeptides. Read about translation.)
Which component is not directly involved in translation? A) mRNA B) DNA C) tRNA D) ribosomes E) GTP
DNA
The average length of a transcription unit along a eukaryotic DNA molecule is about 27,000 nucleotide pairs, whereas an averaged-sized protein is about 400 amino acids long. What is the best explanation for this fact?
Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated. (Most of these noncoding sequences are interspersed between coding segments of the gene and thus between coding segments of the pre-mRNA. Read about split genes and RNA splicing.)
Your body contains tens of thousands of different proteins, each with a specific structure and function. The unique three-dimensional shape of each of these diverse proteins is based on several superimposed levels of structure. Which of the following is an accurate statement about proteins?
The primary structure of a protein is the order of amino acids in a polypeptide, as coded for by the DNA of a gene. (The primary structure of a protein is its sequence of amino acids, which dictates secondary and tertiary structure. Secondary structure, such as αα helices or ββ pleated sheets, is the result of hydrogen bonds between the repeating constituents of the polypeptide backbone. Tertiary structure is the overall shape of a polypeptide resulting from interactions between the side chains (R groups) of the various amino acids, and quaternary structure is the overall protein structure that results from the aggregation of two or more polypeptide chains into one functional macromolecule.)
In the diagram below, the green unit represents _____.
The promoter
