Mutation

Concept: Point Mutations

8m

Concept: Frameshift Mutations and Chromosomal Mutations

5m

Mutation Additional Practice Problems

A random mutation event has lead to the deletion of a nucleotide within the translated region of a particular gene. How would the resulting protein be different from the unmutated for of the gene? Explain your answers in 2-3 sentences.

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For the given sequence 5' - GGAGCUCGUUGUAUU - 3'

A. Is this sequence RNA or DNA? How can you tell?

B. Which amino acids are encoded, if the reading frame is as shown, starting from the correct end?

C. What would be the effect on the amino acid sequence if the sequence were changed to 5' GGAGACUCGUUGUAUU -3'? Explain why the amino acid sequence changes.

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Predict the potential effect of a particular point mutation on the structure and function of a protein.

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Explain why a point mutation in a gene may or may not cause a change in the primary sequence of a protein.

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Name the three types of base substitution mutations and list the consequence of each type?

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Which of the following statements are true about mutations at the 7q11.23?

A. Some individuals with autism have extra copies of this genetic region.

B. This genetic region has a big impact on social ability.

C. Individuals who have a deletion at this genetic region have Williams-Beuren syndrome, a disease that makes people especially social and outgoing.

D. This genetic region has been identified in all the autism children studied.

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What is a missense mutation?

A. a mutation whose effect is not yet known.

B. a mutation that changes a codon that specifies an amino acid to one that terminates translation.

C. a mutation that changes a codon to a synonymous codon.

D. a mutation that alters the reading frame of the gene.

E. a mutation that results in a different amino acid in a protein.

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A ______ mutation is one that leads to premature insertion of a stop codon within an ORF.

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In the strand below, a mutation occurs at the 8th nucleotide. The nucleotide is deleted. Transcribe then translate the strand to see what happens to the protein.

original : 3' - TAG CTG AAT TGC AGT GCC ATC GATG - 5'

mutated : 3' - TAG CTG ATT GCA TTG CCA TTG ATG - 5'

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Describe how a mutation can lead to large scale changers in the structure of an organism.

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What type of mutation would be caused if three bases were deleted from the original DNA strand? Would this cause an amino acid to be lost?

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What type of mutation would be caused if two bases are deleted from the original DNA strand? What would happen to the protein?

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Define the following:  

a. Proband 

b. Penetrance 

c. Non-sense mutation

d. Trisomy 

e. Homologous chromosomes 

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UV light damages DNA. What bases in the DNA specifically does it damage? What chemical changes that occur, or how does the physical structure of the DNA change? How do these changes kill cells?

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Below is the active site of chymotrypsin. Which mutation would have a greater effect on protein function: replacing Asp102 with glutamine or glutamic acid? Why?

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Would a random mutation in a coding region of the genome or a random mutation that occurs during transcription/mRNA processing be worse for the cell/organism overall? Explain.

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Given the DNA sequences below of coding strands, identify and underline the mutation in each. What effect did each DNA mutation have on the final protein products. What type of mutation occurred (synonymous, non-synonymous, nonsense, nonstop)? Explain. Original DNA Sequence

5’ – A T G T T T C T G G T C A A T T G C G C A G G T C C A A C C T A G – 3’

Mutated Sequences:

A. 5’ – A T G T T T T T G G T C A A T T G C G C A G G T C C A A C C T A G – 3’

B. 5’ – A T G T T T G T G G T C A A T T G C G C A G G T C C A A C C T A G – 3’

C. 5’ – A T G T T T C T G G T C A A T T G C G C A G G T C C A A C C T A A – 3’

D. 5’ – A T G C T T T C T G G T C A A T T G C G C A G G T C C A A C C T A G – 3’

E. 5’ – A T G T T T C T G G T C A A T T A G C G C A G G T C C A A C C T A G – 3’

F. Which of the above mutations do you think would be more deleterious to the cell/organism? Explain your reasoning. 

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Why are point mutations in the third nucleotide of a codon less likely to cause the production of a non-functional protein? Is this also true for frameshift mutations? Why or why not?

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Base substitution mutations and frame-shift mutations: 

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 (frame-shift, base substitution, or neither), as compared to the correct sequence shown above. Sort the items into the appropriate bins. 

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Which of the following could NOT introduce a premature stop codon in mRNA?

a. insertion of an incorrect nucleotide by RNA polymerase during transcription

b. a mutation in the coding sequence within the DNA

c. a mutation in the promoter sequence within the DNA

d. a mistake during splicing that leads to retention of an intron

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A protein-coding gene is diagrammed below, with 4 exons (blue boxes) and 3 introns. A researcher has isolated four different mutant alleles of this gene, designated A, B, C, and D. Each of the alleles has a different four-basepair insertion; their locations within the gene are shown by the red triangles in the figure. Which insertion - A, B, C, or D - is likely to have the biggest effect on protein function? Explain.

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How might a mutation cause a change in protein function? Are there any instances when a mutation can result in no change to an organism? 


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What would occur if a mutation caused an aminoacyl-tRNA synthetase to recognize both its normal amino acid and a different one?

a. Translation would occur normally.

b. All codons would be misread.

c. One or more codons would sometimes be misread.

d. One or more codons would always be misread.

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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.

        

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Which of the following mutations would be most likely to have a harmful effect on an organism?

a. a deletion of three nucleotides near the middle of a gene
b. a single nucleotide insertion downstream of, and close to, the start of the coding sequence
c. a single nucleotide deletion near the end of the coding sequence
d. a single nucleotide deletion in the middle of an intron
e. a base-pair substitution

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Both nonsense mutations and frameshift mutations can cause mutant proteins to be shorter than normal. Explain how the same general type of effect on protein structure is caused by these two different types of mutations.


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How do splice-site mutations differ from nonsense mutations?

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Compare the consequences of germline mutations to somatic mutations.

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Describe four types of point mutations:transitions, transversions, deletions, and additions.

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Explain how errors in DNA replication can cause mutations.

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Explain why deletion of a single nucleotide in a gene generally results in more severe defects in the polypeptide than a point mutation that changes a single nucleotide.

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List four genes whose mutations are associated with cancer. For each gene briefly describe: 1) Their normal functions, including the related signaling pathways and cell behaviors; 2) Their oncogenic roles: the effects of their mutants to cell behaviors in cancers. (Tow genes whose coding proteins are closely associated with each other will only be counted as One.)

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Define "mutation" and describe its potential consequences.

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A somatic mutation is a mutation that occurs in cells that give rise to gametes. 

a. True

b. False

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Translocation during meiosis is not a cause of mutation. 

a. True

b. False

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Which mutation in DNA would lead to the change of a single amino acid in a protein? 

a. A nonsense mutation

b. A one base deletion

c. A one base insertion

d. A missense mutation

e. A frameshift

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What type of mutation has occurred in the following?
Normal allele 5' – GGAAUGAAACAGGAACCC – 3'
Mutant allele 5' – GGAAUGAAAUCAGGAACCC – 3' 

a. Insertion of one base

b. Substitution

c. Deletion of one base

d. Insertion of two bases

e. Deletion of two bases

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What type of mutation has occurred in the following?
Normal allele 5' – GGAAUGAAACAGGAACCC – 3'
Mutant allele 5' – GGAAUGAAACAGGUACCC – 3' 

a. Substitution

b. Insertion of one base

c. Deletion of one base

d. Insertion of two bases

e. Deletion of two bases

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Using the genetic code shown here, predict what type of mutation has occurred in the hemoglobin sickle cell anemia allele.
Normal allele 5' – GGAAUGAAACAGGAACCC – 3'
Mutant allele 5' – GGAAUGAAACAGGUACCC – 3' 

a. A point mutation, Val to Glu

b. A frame shift

c. Addition of a new stop codon

d. A point mutation, Glu to Val

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In a "frameshift" mutation: 

a. The codon that mutates causes a change in the amino acid specified

b. The codon that mutates causes a stop codon to occur instead of the placement of an amino acid

c. The mutation does not occur in a codon

d. May be caused by an addition or deletion of one or more nucleotides

e. The mutation is not in DNA

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In a "silent" mutation: 

a. The codon that mutates causes a change in the amino acid specified

b. The codon that mutates does not cause a change in the amino acid specified

c. The codon that mutates causes a stop codon to occur instead of the placement of an amino acid

d. The mutation does not occur in a codon

e. The mutation is not in DNA

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In a "missense" mutation: 

a. The codon that mutates does not cause a change in the amino acid specified

b. The codon that mutates causes a change in the amino acid specified

c. The codon that mutates causes a stop codon to occur instead of the placement of an amino acid

d. The mutation does not occur in a codon

e. The mutation is not in DNA

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In a "nonsense" mutation: 

a. The codon that mutates does not cause a change in the amino acid specified

b. The codon that mutates causes a change in the amino acid specified

c. The codon that mutates causes a stop codon to occur instead of the placement of an amino acid

d. The mutation does not occur in a codon

e. The mutation is not in DNA

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Mutations may be caused by: 

a. Errors in replication

b. Exposure to radiation

c. Exposure to chemicals

d. Breakage of chromosomes

e. All are correct

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Which point mutation would be most likely to have a catastrophic effect on the functioning of a protein?

a. a base substitution

b. a base deletion near the start of the coding sequence

c. a base deletion near the end of the coding sequence, but not in the terminator codon

d. deletion of three bases near the start of the coding sequence, but not in the initiator codon

e. a base insertion near the end of the coding sequence, but not in the terminator codon

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