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| 1 | |
True or False
- The first level of compaction of DNA consists of DNA winding around histones to form small nucleosomes.
- In DNA, most satellite sequences are found in telomeres.
- One of the functions of a centromere is to hold sister chromatids together.
- In higher eukaryotes, kinetochores attach to multiple spindle fibers.
- Barr bodies are seen in a Turner's (XO) female.
|
| | A) | T,T,T,F,F |
| | B) | T,F,T,T,F |
| | C) | F,F,F,T,T |
| | D) | F,F,T,T,F |
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| 2 | |
Structures showing differential staining under light microscopy are known as:
|
| | A) | centromeres |
| | B) | telomeres |
| | C) | ARS |
| | D) | satellite DNA |
| | E) | G bands |
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| 3 | |
Structure allowing replication in yeast are known as:
|
| | A) | centromeres |
| | B) | telomeres |
| | C) | ARS |
| | D) | satellite DNA |
| | E) | G bands |
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| 4 | |
The sites of attachment of kinetochores lie in:
|
| | A) | centromeres |
| | B) | telomeres |
| | C) | ARS |
| | D) | satellite DNA |
| | E) | G bands |
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| 5 | |
Local helix unwinding is necessary for:
|
| | A) | imprinting |
| | B) | decondensation |
| | C) | X-inactivation |
| | D) | position effect variegation |
| | E) | transcription |
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| 6 | |
Barr bodies result from:
|
| | A) | telomerase activity |
| | B) | decondensation |
| | C) | X-inactivation |
| | D) | position effect variegation |
| | E) | transcription |
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| 7 | |
A process facilitating mRNA synthesis is:
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| | A) | telomerase activity |
| | B) | decondensation |
| | C) | X-inactivation |
| | D) | position effect variegation |
| | E) | transcription |
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| 8 | |
Proximity to heterochromatin can cause:
|
| | A) | telomerase activity |
| | B) | decondensation |
| | C) | X-inactivation |
| | D) | position effect variegation |
| | E) | transcription |
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| 9 | |
A form of DNA that tends to be transcriptionally inactive is exemplified by:
|
| | A) | nucleosome |
| | B) | 300 angstrom fiber |
| | C) | chromosome puff |
| | D) | euchromatin |
| | E) | heterochromatin |
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| 10 | |
The core histones provide the structural basis for the:
|
| | A) | nucleosome |
| | B) | 300 angstrom fiber |
| | C) | chromosome puff |
| | D) | euchromatin |
| | E) | heterochromatin |
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| 11 | |
A region of heavily transcribed DNA in a polytene chromosome is seen as:
|
| | A) | nucleosome |
| | B) | 300 angstrom fiber |
| | C) | chromosome puff |
| | D) | euchromatin |
| | E) | heterochromatin |
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| 12 | |
rRNA transcription is associated with:rRNA transcription is associated with:
|
| | A) | histone |
| | B) | non-histone protein |
| | C) | kinetochore |
| | D) | telomerase |
| | E) | nucleolus |
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| 13 | |
A ribonucleoprotein is exemplified by:
|
| | A) | histones |
| | B) | non-histone protei |
| | C) | kinetochore |
| | D) | telomerase |
| | E) | nucleolus |
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| 14 | |
Positively charged subunits around which the DNA helix is wrapped are known as:
|
| | A) | histones |
| | B) | non-histone protein |
| | C) | kinetochore |
| | D) | telomerase |
| | E) | nucleolus |
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| 15 | |
A histone gene is mutated such that a positively charged amino acid is substituted with a negatively charged one. What is the most likely result?
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| | A) | histone will be transported to nucleolus |
| | B) | the histone will bind DNA better |
| | C) | the histone will bind DNA less well |
| | D) | formation of Barr bodies will be enhanced |
| | E) | gene expression will be inhibited |
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| 16 | |
Which of the following is not an element of a YAC?
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| | A) | telomere sequences |
| | B) | suitable selectable markers |
| | C) | chromocenter |
| | D) | a yeast centromere |
| | E) | a yeast origin of replication |
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| 17 | |
A DNase hypersensitive (DH) site may indicate:
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| | A) | a transcribed region |
| | B) | the 5' end of a gene |
| | C) | a region unwound from nucleosomes |
| | D) | a & b |
| | E) | all of the above |
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| 18 | |
Barr body formation usually occurs:
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| | A) | about two weeks after zygote formation |
| | B) | during adolescence |
| | C) | by condensation of the paternal X chromosome |
| | D) | by condensation of the maternal X chromosome |
| | E) | none of the above |
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| 19 | |
Which of the following is not a feature of Drosophila polytene chromosomes?
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| | A) | ~1024 DNA double helices |
| | B) | ~1024 telomeres |
| | C) | ~1024 centromeres |
| | D) | chromosomes fused at chromocenter |
| | E) | found in salivary gland cells |
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| 20 | |
Arrange the following in increasing order of compactness:
A. nucleosome
B. radial-loop scaffold
C. 300 angstrom fiber
D. DNA helix
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| | A) | A,C,B,D |
| | B) | C,A,B,D |
| | C) | D,C,A,B |
| | D) | C,D,A,B |
| | E) | D,A,C,B |
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| 21 | |
You are trying to clone ARSs from yeast. To initiate the cloning process, you fragment yeast genomic DNA using partial digestion or sonication and create a library by cloning the fragments into a plasmid vector that carries the URA+ gene, but not an ARS. Uracil (ura) is required for growth. You then use this library to transform Ura- yeast cells and plate them onto test media. The results are shown in the table below:
| Number of colonies per ml | Medium |
| | ura+ | ura- | |
| |
vector only |
2 X 106 |
10 | |
vector + library |
2 X 106 |
1.8 X 106 |
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Did your cloning experiment work? From which vector + library plate (ura+ or ura-) are you most likely to find a clone containing an ARS?
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| | A) | yes; ura+ |
| | B) | yes; ura+
yes; ura- |
| | C) | no; ura+ |
| | D) | no; ura- |
| | E) | yes; either is equally likely |
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| 22 | |
You are using a DNase hypersensitivity test to monitor chromosome condensation (and thus activity) of a gene that resides in the region of DNA shown below:
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Chromatin is treated briefly with DNase, the DNase is removed and the DNA is then digested to completion with XhoI (X). DNA fragments are run on a gel, transferred to a nylon membrane, and then probed with a DNA fragment from the region (see above). The results from the Southern blot are shown below:
| No DNase | | DNase | |
12 kb |
__ | |
__ | |
10 |
__ | |
__ | | | | | |
8 |
__ | | | |
6 |
__ | |
__ | |
5 |
__ | |
__ | | | | | | |
4 | | |
__ | | | | | | |
3 | | |
__ | | | | | | |
1 | | |
__ | | | | | |
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How many DNase hypersensitive (DH) sites are in this region? Within which XhoI fragment are they?
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| | A) | 2; 4 kb |
| | B) | 2; 3 kb |
| | C) | 2; 8 kb |
| | D) | 3; 4 kb |
| | E) | 3; 8 kb |
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| 23 | |
One property of position-effect variegation is that heterochromatin (highly condensed and inactive) can spread over more than 1000 kb of previously euchromatic chromatin. A rearrangement in fruit flies allows you to investigate whether this process can "skip" over genes as it spreads along the chromosome. This particular rearrangement has brought both the white+ gene and the roughest+ genes near heterochromatin.
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Wild type flies with both white+ (w+) and roughest (rst+) alleles have red eyes and smooth eye surfaces. Flies mutant for these two genes have white eyes and smaller, rough-surfaced patches on their eyes. Flies carrying the rearrangement shown above were examined for the presence of variegated sectors in their eyes. On the basis of your observations, you conclude that heterochromatin spreads without skipping genes. If this is true, what pattern did you not see?
|
| | A) | red, smooth sectors |
| | B) | white, smooth sectors |
| | C) | white, rough sectors |
| | D) | red, rough sectors |
| | E) | all 4 patterns were observed |
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| 24 | |
Women who were known to be carriers of the X-linked, recessive, hemophilia gene were studied in order to determine the amount of time required for the blood clotting reaction. It was found that the time required for clotting was extremely variable from individual to individual. The values obtained ranged from normal clotting time at one extreme, all the way to clinical hemophilia at the other extreme. What is the most probable explanation for these findings?
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| | A) | position effect variegation |
| | B) | X-inactivation |
| | C) | telomerase |
| | D) | mitotic instability |
| | E) | DNase I hypersensitivity |
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| 25 | |
You are trying to map the location of a yeast centromere within the 8.5 kb region of DNA shown below using a mitotic stability assay.
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DNA fragments from the region above were cloned into a yeast URA+ ARS vector and then tested for mitotic stability. This assay consists of growing a transformed cell culture without selection for the plasmid and then determining the percent of URA+ colonies remaining after 20 generations of growth. Based on the results indicated below, which fragment(s) contain(s) the centromere?
| | Construct | % Ura+ colonies after
20 generations |
| |
vector only |
0.8 | |
vector + 8.5 PstI |
85 | |
vector + 4.5 PstI |
83 | |
vector + 4.0 PstI |
0.4 | |
vector + 3.0 EcoRI-PstI |
0.8 | |
vector + 1.5 PstI-EcoRI |
75 | |
vector + 1.0 PstI-EcoRI |
82 | |
vector + 0.5 EcoRI |
0.5 |
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|
| | A) | 4.0 PstI |
| | B) | 1.0 PstI-EcoRI |
| | C) | 0.5 EcoRI |
| | D) | 3.0 EcoRI-PstI |
| | E) | vector |
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