Mastering Biology Chapter 17
The following eukaryotic structural gene contains two introns and three exons.The table below shows four possible mRNA products of this gene. Use the labels to explain what mutation(s) may have resulted in each mRNA.Drag the correct label to each location in the table. Labels may be used once, more than once, or not at all.
1. Mutation in a splicing signal sequence in the intron 2 2. mutation in the gene's promoter sequence 3. mutations in splicing signal sequences in both intron 1 and intron 2 4. no mutation in any splicing signal sequence
Life as we know it depends on the genetic code: a set of codons, each made up of three bases in a DNA sequence and corresponding mRNA sequence, that specifies which of the 20 amino acids will be added to the protein during translation. Imagine that a prokaryote-like organism has been discovered in the polar ice on Mars. Interestingly, these Martian organisms use the same DNA → RNA → protein system as life on Earth, except that there are only 2 bases (A and T) in the Martian DNA, and there are only 17 amino acids found in Martian proteins. Based on this information, what is the minimum size of a codon for these hypothetical Martian life-forms?
5 bases
The direction of synthesis of an RNA transcript is _____.
5' —> 3'
Assuming all other numbers of interest fall into the normal range, which of the following people is most likely to be successfully treated with the statin drug Lipitor?
A 57 year old man with high LDL.
Which of the following statements about mutations is false?
A knock-out mutation results in a total absence of the mutated protein.
Transcription begins at a promoter. What is a promoter?
A site in DNA that recruits the RNA Polymerase
At which site do new aminoacyl tRNAs enter the ribosome during elongation?
A-site
If a mutated DNA sequence produces a protein that differs in one central amino acid from the normal protein, which of the following kinds of mutations could have occurred?
An addition mutation and a deletion mutation.
Which of these is a tRNA?
B
What determines which base is to be added to an RNA strand during transcription?
Base pairing between the DNA template strand and the RNA nucleotides
Which of the following appears to be true? Only LDL plays a role in heart disease. Neither LDL nor triglycerides play a role in heart disease. Both LDL and triglycerides play a role in heart disease. Only triglycerides play a role in heart disease.
Both LDL and triglycerides play a role in heart disease.
The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____.
CUG
Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?
Complementary
In the diagram below, the two blue strands represent _____.
DNA
If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?
Deletion
Which of the following mutations would likely be most dangerous to a cell?
Deletion of one nucleotide
Ribosomes provide the scaffolding on which tRNAs interact with mRNA during translation of an mRNA sequence to a chain of amino acids. A ribosome has three binding sites, each of which has a distinct function in the tRNA-mRNA interactions. Drag the appropriate tRNAs to the binding sites on the ribosome to show the configuration immediately before a new peptide bond forms. Note that one of the binding sites should be left empty.
E- site empty P- site AUA with three amino acids A- site UCC with one amino acid
True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated
False
If a segment of DNA were replicated without any errors, the replicated strand would have the following sequence of nucleotides: 5' - ACTACGTGA - 3' Sort the following replicated DNA sequences by the type of point mutation each contains (frameshift, base substitution, or neither), as compared to the correct sequence shown above. Sort the items into the appropriate bins.
Frameshift Mutation) 5'-ACTTACGTGA-3' 5'-ACTCGTGA-3" Base substation mutation 5'- ACTAAGTGA-3' 5'-ACTACGTGT-3' neither
Which of these correctly illustrates the pairing of DNA and RNA nucleotides?
GTTACG CAAUGC
What happens to RNA polymerase II after it has completed transcription of a gene?
It is free to bind to another promoter and begin transcription.
Which of the following is true? Triglycerides are a type of cholesterol. LDL is a type of cholesterol. Neither LDL nor triglycerides are types of cholesterol Both LDL and triglycerides are types of cholesterol.
LDL is a type of cholesterol.
During translation, nucleotide base triplets (codons) in mRNA are read in sequence in the 5' → 3' direction along the mRNA. Amino acids are specified by the string of codons. What amino acid sequence does the following mRNA nucleotide sequence specify? 5′−AUGGCAAGAAAA−3′ Express the sequence of amino acids using the three-letter abbreviations, separated by hyphens (e.g., Met-Ser-Thr-Lys-Gly).
Met-Ala-Arg-Lys
Before a molecule of mRNA can be translated into a protein on the ribosome, the mRNA must first be transcribed from a sequence of DNA.
Met-Ser-Cys-His
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?
Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes. A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA. A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.
Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)?
One addition and one deletion mutation.
DNA does not store the information to synthesize which of the following?
Organelles
The initiator tRNA attaches at the ribosome's _____ site.
P
For each protein, identify its targeting pathway: the sequence of cellular locations in which the protein is found from when translation is complete until it reaches its final (functional) destination. (Note that if an organelle is listed in a pathway, the location implied is inside the organelle, not in the membrane that surrounds the organelle.)
PFK---Cytoplasm only insulin---ER-->Golgi-->outside cell
Which of the following processes is an example of a post-translational modification?
Phosphorylation
The four levels of protein structure are primary, secondary, tertiary, and quaternary structure. Review the levels of protein structure by clicking the image below. Drag each label into the appropriate bin depending on whether it applies to primary, secondary, tertiary, or quaternary structure.
Primary Structure- amino acid sequence Secondary Structure- result from hydrogen bonding bestrewn the backbone constituens of the poly peptide, alpha helix, beta pleated sheet Tertiary Structure- the overall shape of a polypeptide, results from interactions between side chains (R groups) of amino acids Quaternary Structure- The aggregation of multiple polypeptide subunits.
In the diagram below, the gray unit represents _____.
RNA polymerase
What name is given to the process in which pre-mRNA is edited into mRNA?
RNA processing
Indicate at which step of the replication-transcription-translation process each type of RNA first plays a role. During which step of the replication-transcription-translation process does each type of RNA first play a role? Drag each item to the appropriate bin. (Not every bin has to be filled.)
Replication- empty Transcription/ RNA-- processing mRNA Translation--tRNA, rRNA
Where does translation take place?
Ribosome
Which of the following steps occurs last in the initiation phase of translation?
The large ribosomal subunit joins the complex.
Which of the following statements best describes the promoter of a protein-coding gene?
The promoter is a nontranscribed region of a gene.
What is meant by translocation?
The ribosome slides one codon down the mRNA.
What is the process called that converts the genetic information stored in DNA to an RNA copy?
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
Suppose that a portion of double-stranded DNA in the middle of a large gene is being transcribed by an RNA polymerase. As the polymerase moves through the sequence of six bases shown in the diagram below, what is the corresponding sequence of bases in the RNA that is produced?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
You have a blood panel done and your triglyceride level is 107. Which of the following is true?
Your level is below that of the average American.
You have a normal APOC3 gene. You eat a very fatty meal. Which of the following is most likely to happen?
Your triglycerides will spike.
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
During RNA processing a(n) _____ is added to the 3' end of the RNA.
a long string of adenine nucleotides
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
In this activity, you will examine two specific nucleotide-pair deletion mutations that affect this region of the CFTR sequence: [delta]F508 and 1660delG. Drag the amino acids to the white targets to indicate what each mRNA codon codes for. (You will probably need to consult the codon table for mRNA.) Drag the blue labels to the blue targets to indicate the effect on the polypeptide's primary structure. Be sure to compare the mutant amino acid sequence to the wild-type sequence above. Labels may be used once, more than once, or not at all.
a) Ile b)Gly c)Val d)Ser e)Phe f)pro g) No frameshift h) frameshift--extensive missense
In this activity, you will examine three different mutations. Drag the white and purple labels to the white targets to indicate what each mutant mRNA codon codes for. (You will probably need to consult the codon table for mRNA .) Drag the pink labels to the pink targets to indicate the type of mutation. Drag the blue labels to the blue targets to indicate the effect on the polypeptide's primary structure. Labels may be used once, more than once, or not at all.
a) Val b) Substitution c) missense d) Glu e) Substitution f) Silent g) Stop h) Substitution i) nonsense
In eukaryotic cells, the processes of protein synthesis occur in different cellular locations. Drag the labels to the appropriate targets to identify where in the cell each process associated with protein synthesis takes place.
a) formation of ribosomal subunits b)attachment of an amino acid to tRNA c)translation of cytoplasmic proteins d)transcription and
Label the four mutated DNA segments shown below according to the type of point mutation each represents. Use the codon table above to determine how each mutation would affect the amino acid coding for each segment. Drag the labels to their appropriate locations to identify the type of point mutation shown.
a) silent mutation b) nonsense mutation c) missense mutation d) Frameshift mutation
Polypeptides are assembled from _____.
amino acids
What enzyme catalyzes the attachment of an amino acid to tRNA?
aminoacyl-tRNA synthetase
Translation occurs in the _____.
cytoplasm
The RNA segments joined to one another by spliceosomes are _____.
exons
True or false? A codon is a group of three bases that can specify more than one amino acid.
false
What is the name of the process shown in the diagram?
initiation (of translation)
RNA processing converts the RNA transcript into _____.
mRNA
Which nucleic acid is translated to make a protein?
mRNA
During RNA processing a(n) _____ is added to the 5' end of the RNA.
modified guanine nucleotide
Spliceosomes are composed of _____.
snRNPs and other proteins
Use the table to sort the following ten codons into one of the three bins, according to whether they code for a start codon, an in-sequence amino acid, or a stop codon. Drag each item to the appropriate bin.
start/methionine- AUG Stop codon- UAA, UAG, UGA Amino acid- GCA, ACU, CAC, AAA AUC, UGC
Sort each description by the type of RNA it describes. Drag each item to the appropriate bin.
tRNA- Contains an anticodon, has amino acids covalently attached mRNA- specifies the amino acid sequence for a protein, contains exons rRNA is a component of ribosomes, is the most abundant form of RNA
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
In the diagram below, the green unit represents _____.
the promoter
RNA plays important roles in many cellular processes, particularly those associated with protein synthesis: transcription, RNA processing, and translation. Drag the labels to the appropriate bins to identify the step in protein synthesis where each type of RNA first plays a role. If an RNA does not play a role in protein synthesis, drag it to the "not used in protein synthesis" bin.
transcription/RNA processing- pre-mRNA, mRNA, snRNA translation- rRNA, tRNA
What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?
translation
If the sequence ATGCATGTCAATTGA were mutated such that a base were inserted after the first G and the third T were deleted, how many amino acids would be changed in the mutant protein?
two
