1. Mutations and defects in chromosomal structure January 2009

2. Types of Mutations

3. How do most mutations arise?
A. They are caused by environmental stress and are a response to it
B. They are random events that can be caused by many different things
C. They preprogrammed into the genome to occur in response to specific signals
D. Mutations almost never happen because DNA can repair itself
Fall ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Drs. Michelle Smith and Ken Krauter
95% correct in Ken Krauter’s course 3

4. A change in DNA sequence that causes a change in phenotype
What is a mutation?
A change in DNA sequence that causes a change in phenotype
A change in DNA sequence that is passed to a cell’s progeny
Any change in DNA sequence
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman

5. How do mutations arise?
Experiment: expose bacteria to bactericide; wild type cells do not survive, but there are some colonies on the plates. These colonies have mutations that allow them to grow on bactericide.
How did the mutations arise?
A) Exposure to bactericide causes mutations – creates cells that are resistant.
B) Mutations happen randomly – some mutations just happen to make cells resistant to bactericide.
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman

6. Luria-Delbruck Experiment
What do the results of this experiment mean?
Mutations are more frequent when cells are exposed to bactericide
Mutations likely occurred after exposure to the bactericide
Mutations likely occurred before exposure to the bactericide
Random mutations likely occurred before the cells were exposed to bactericide.
Some cells acquired mutations that allowed them to grow on bactericide.
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman

7. If depurination occurs 1000 times/hour in humans, why
don’t humans have more genetic diseases (mutations)?
A) most of the mutations are in parts of the genome that are not transcribed
to mRNA, so the mutations have little effect.
B) most depurinations are fixed by DNA repair enzymes.
C) most depurinations will occur in cells that are not part of the germline, so they
will not cause disease.
D) the redundancy of the genetic code will prevent the depurinations from changing
the protein sequence and causing disease.
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman

8. All of the above will lead to nonfunctional proteins
Which type of mutation is most likely to lead to the formation of a nonfunctional protein?
A silent mutation
A frame shift mutation
A missense mutation
All of the above will lead to nonfunctional proteins
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman

9. A. nucleotides were deleted B. additional nucleotides were added
A type of human dwarfism results from the production of mutant SHR-1 protein. You look at the length of the mutant SHR-1 and the normal (wild-type) SHR-1 protein, and discover that the mutant SHR-1 protein has fewer amino acids. What do you expect to find when you examine the DNA sequence?
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Nancy Guild and Dr. Michelle Smith
87% correct
A. nucleotides were deleted
B. additional nucleotides were added
C. one nucleotide was changed
D. without additional information, any of the above are possible

10. You are studying a gene called Ant-1
You are studying a gene called Ant-1. You discover an insertion of one nucleotide in a mutant Ant-1 gene. When you compare the wild-type Ant-1 protein and the mutant Ant-1 protein, you expect that:
The wild-type Ant1 protein will be longer than the mutant Ant-1 protein
The mutant Ant-1 protein will be longer than the wild-type Ant 1 protein
The wild-type Ant-1 protein and the mutant Ant-1 protein will be the same length
Answer A and B
All of the above
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Nancy Guild and Dr. Michelle Smith
49% correct

11. ATG= Met GAG= Glu TGA =Stop GAA= Glu TAA= Stop CAA= Gln CAG = Gln
The following DNA sequence corresponds to the two extreme ends of a gene’s coding regions:
5’ ATG-GAA//CAG-TGA 3’
Each codon is separated by a dash and the middle of the gene is represented by “//”.
Referring to the codons listed above, which of the following sequence changes is likely to interfere most with the function of this gene?
A. 5’ ATG-GAA//CAA-TGA 3’
B. 5’ ATG-TAA//CAG-TGA 3’
C. 5’ ATG-GAG//CAG-TGA 3’
D. (a.) and (b.) are equally likely to interfere with the function of this gene
E. (b.) and (c.) are equally likely to interfere with the function of this gene
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Nancy Guild and Dr. Michelle Smith
85% correct

12. You have isolated a conditional mutation in Neurospora that has the following phenotype: At 30 degrees it can synthesize DNA, at 42 degrees no DNA is synthesized and the cells die. This mutation is most likely a
a. Nonsense mutation
b. Missense mutation
c. Frameshift mutation
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Nancy Guild and Dr. Michelle Smith
63% correct

13. Let’s say you lived in a world where there was no physical (UV light and X-ray), and no chemical mutagens. Would your DNA undergo mutations?
Yes No
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Nancy Guild and Dr. Michelle Smith
96% correct

14. You heard on the news that grilling steak can create
carcinogens and cause cancer, so you decide to test the hypothesis with the Ames Test
+ control
sodium azide
a known carcinogen
- control
no sample
experimental –
small piece of
grilled steak
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman
Are the colonies on the experimental plate likely to be revertants?
A) yes
B) no

15. You heard on the news that grilling steak can create
carcinogens and cause cancer, so you decide to test the hypothesis with the Ames Test
+ control
sodium azide
a known carcinogen
- control
no sample
experimental –
small piece of
grilled steak
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman
Are the colonies on the negative control plate likely to be revertants?
A) yes
B) no

16. Test substance + rat liver enzyme + distilled water 500
Test substance + distilled water
distilled water
rat liver enzymes
positive control
negative control
The test substance is:
a mutagen
a mutagen, but only when metabolized
not a mutagen
can’t tell – there is contamination in the experiment
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman

17. C A T C G G T A G C C A T X G G T A C C A T C G C A T C G G T A C
Depurination
C A T C G
G T A C
apurinic site
G T A G C
Depurination is the removal of a purine base.
After a depurination, how many (of the 4) replicated DNA strands
are likely to be mutant? 1 2 3 4
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman

18. This can explain the following mode of inheritance
When the mutation 21 is present, wild type protein no longer functions.
This can explain the following mode of inheritance
dominant (Aa or AA = disease)
recessive (aa = disease)
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Tin Tin Su and Dr. Michelle Smith
84% correct 18

19. Characterization of Mutants (complementation)

20. Current Biology Journal
Study published
Jan 8, 2008
Current Biology Journal
You study eye formation using Mexican cave-dwelling blind fish. You know that blindness is a trait controlled by multiple genes and inherited in a recessive manner.
A blind fish from a true-breeding line in one cave was crossed to a blind fish from a true-breeding line in another cave. If the mutation that cause blindness is in the same gene in two fish, you should see
A. None of the offspring are blind
B. 25% of the offspring are blind
C. 50% of the offspring are blind
D. 75% of the offspring are blind
E. All of the offspring are blind
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Tin Tin Su and Dr. Michelle Smith
86% correct 20

21. How many genes did you mutate?
You isolate 3 mutant strains of rII, labeled You coinfect E. coli K12  with pairwise combinations (1&2, 1&3 etc.) of the 3 mutant strains and get the following results: 1 2 3 + -
How many genes did you mutate? 1 2 3 4
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Nancy Guild and Dr. Michelle Smith
73% correct 21

22. How many genes did you mutate?
Oops, you just found another rII mutant strain on your laboratory bench. So you expand your complementation test to include the 4 mutant strains and get the following results: 1 2 3 4 + -
How many genes did you mutate? 1 2 3 4
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Nancy Guild and Dr. Michelle Smith
51% correct 22

23. 1 2 3 4 5 6 1 - + - - + + 2 - + + + + 3 - - + + 4 - + + 5 - + 6 -
Complementation Data Neurospora Auxotrophs (Haploids) Mated with Each Other and Plated on Minimal Plates
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Nancy Guild and Dr. Michelle Smith
88% correct
Strains 1-6 are all arg- auxotrophs, how many genes? 1 2 3 4 5 23

24. CSU has hired you to generate green ram mascots
CSU has hired you to generate green ram mascots. You mutate a bunch of rams and get 4 that are green because of recessive mutations. You carry out crosses between all the rams (all rams can mate with each other, don’t worry about mascot sex) and produce the following results where a "-" means mutant green rams were produced and a "+" means wild-type white rams were produced. 1 2 3 4 + ? -
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Tin Tin Su and Dr. Michelle Smith
80% correct
Which statement is correct?
1 crossed with 3 will produce a green ram
1 crossed with 3 will produce a white ram 24

25. UNC has hired you to generate gold bear mascots
UNC has hired you to generate gold bear mascots. You mutate a bunch of bears and get 4 that are gold because of recessive mutations. You carry out crosses between all the bears (all bears can mate with each other, don’t worry about mascot sex) and produce the following results where a "-" means mutant gold bears were produced and a "+" means wild-type brown bears were produced. 1 2 3 4 - + ?
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Tin Tin Su and Dr. Michelle Smith
76% correct
Which statement is correct?
1 crossed with 4 will produce a gold bear
1 crossed with 4 will produce a brown bear 25

26. phage assembly pathway
Next, you want to determine
how many different genes your
mutants represent, so you perform
a complementation test.
Which is/are true in your complementation test?
A) if the mutations of the parents are in the same gene,
plaques will not form.
B) If the mutations of the parents are in the same gene,
plaques will form.
C) if the mutations of the parents are in different genes,
D) Both A and C are true.
E) Both B and C are true.
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman

27. Complementation Test Results1 - + 2 3 4 5 6
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman
How many different genes do your 6 mutants represent?
A) C) 4
B) D) 3

28. Complementation data can be presented in a grid:
Here’s a grid for six strains showing the same mutant phenotype:
Spring ’06 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Mark Winey
How many complementation groups are there?
A B C D E. 5

29. Chromosomal Structure Mutations (Translocations, inversions, and duplications)

30. Chromosome arrangement of the female translocation carrier
Metaphase of meiosis I (homologues segregate)
Which color signals would represent balanced gametes produced by meiosis
of the above translocated chromosomes?
gamete 1: orange, (red and green) gamete 2: (orange and green), red
gamete1: orange, red gamete 2: (orange and green), (green and red)
gamete 1: red, (red and green) gamete 2: (orange and green), orange
Spring ’08 Clicker Question used in MCDB 2150, Principles of Genetics, written by Dr. Christy Fillman