Which of the following did Erwin Chargaff observe? A) Base composition changes a
ID: 55010 • Letter: W
Question
Which of the following did Erwin Chargaff observe?
A)
Base composition changes as the organism ages.
B)
Base composition of DNA does not vary from one species to another.
C)
In all species the number of adenines equals the number of guanines.
D)
In all species A + T = G + C.
E)
DNAs isolated from different tissues of the same species have the same base composition.
The melting temperature (Tm) of a DNA duplex is:
A)
the temperature at which double-stranded nucleic acids degrade into free nucleotides.
B)
the temperature at which double-stranded DNA is too single-stranded to ever renature back to double strands.
C)
the temperature at which double-stranded DNA is completely melted.
D)
the temperature at which double-stranded DNA has become 50% single-stranded.
E)
the temperature at which double-stranded DNA begins to melt.
Given your knowledge and the descriptions of each of these methods, which of the following does NOT rely on the ability of nucleic acids to hybridize with each other?
A)
Southern blotting for the detection of specific DNA fragments that have been separated by gel electrophoresis.
B)
Colony blot hybridization to identify a specific sequence from a collection of sequences that have been inserted into bacteria.
C)
Northern blotting for the detection of specific RNA fragments that have been separated by gel electrophoresis.
D)
A DNA oligonucleotide microarray incubated with probes made from cDNA.
E)
Western blotting for the detection of specific proteins that have been separated by gel electrophoresis.
Which of the following is a possible reason why DNA uses thymine instead of uracil?
A)
Cytidine is deaminated to uracil so it would be difficult for any repair mechanism to differentiate between uracil that belongs in the sequence and uracil that resulted from deamination.
B)
Adenine is deaminated to uracil so it would be difficult for any repair mechanism to differentiate between uracil that belongs in the sequence and uracil that resulted from deamination.
C)
When uracil is bound to a deoxyribose it will become more reactive, forming covalent bonds with other bases.
D)
None of the above.
Which of the following is an enzyme used in cloning to break covalent bonds?
A)
DNA ligase
B)
Restriction endonuclease
C)
Reverse transcriptase
D)
DNA polymerase I
E)
Alkaline phosphatase
Which of the following could you use to remove the 5' phosphates after cleavage of a plasmid with a single type of restriction enzyme to ensure that the plasmid would not simply fuse back together upon addition of ligase?
A)
Reverse transcriptase
B)
Alkaline phosphatase
C)
DNA ligase
D)
DNA polymerase I
E)
Restriction endonuclease
Which of the following would you use to create a cDNA library that you would not use for a genomic library?
A)
Alkaline phosphatase
B)
Reverse transcriptase
C)
Restriction endonuclease
D)
DNA ligase
E)
DNA polymerase I
A plasmid vector typically has which of the following features?
A)
An origin of replication
B)
A selectable marker to ensure that the only bacteria growing contain the intact or recombinant vector.
C)
Unique restriction sites for insertion of DNA.
D)
Small size to facilitate entry into the cell and biochemical manipulation of the DNA.
E)
All of the above are features of plasmid vectors.
Which of the following is FALSE of genomic or cDNA libraries?
A)
Genes represented in cDNA libraries include control sequences that direct transcription.
B)
cDNA libraries contain cDNAs made from mRNA.
C)
Genomic libraries contain fragments of genomic DNA that are generated by partial digests with restriction enzymes.
D)
Genomic libraries usually contain large fragments and are likely to be constructed in YAC or BAC vectors.
E)
cDNA libraries contain sequences from expressed genes only.
Which of the following is NOT a typical component of a polymerase chain reaction (PCR)?
A)
dNTPs
B)
DNA containing the sequences to be amplified
C)
DNA ligase to connect the fragments together
D)
Primers complementary to each end of the sequence to be amplified
E)
Heat stable Taq polymerase
How can a fusion protein be formed?
A)
Site-directed mutagenesis where a fragment is replaced with a synthetic sequence containing the altered DNA sequence.
B)
Two proteins can recombine in the bacterial cell to form a new hybrid protein.
C)
Portions of two different genes are ligated together to create a new hybrid gene. When expressed the gene product is a fusion of the two gene products.
D)
Using oligonucleotide-directed mutagenesis to introduce specific mutations that cause the expressed protein to fuse to other proteins.
E)
A portion of the gene can be removed to form a shorter gene and therefore a shorter protein.
Why is green fluorescent protein (GFP) so useful in visualizing fusion proteins in eukaryotes?
A)
The GFP protein recognizes and binds to fusion proteins allowing the location of the fusion protein to be determined.
B)
The reaction is only dependent on the presence of GFP and one other cofactor.
C)
It is easily cloned and expressed in bacterial cells.
D)
The presence of just a few molecules of GFP fusion proteins can be sufficient for observing the proteins microscopically allowing the study of its location and movements in the cell.
E)
It is derived from fire flies, which are easy to cultivate in the lab.
You wish to determine the cellular location of a protein but unfortunately it is not particularly antigenic (can t develop a strong antibody response). How could you solve this problem?
A)
Create a fusion protein with an epitope tag that can be visualized by incubation with fluorescently tagged antibody to the epitope.
B)
Create a fusion with green fluorescent protein (GFP).
C)
Express the protein as a fusion with biotin. The addition of GFP will cause fluorescence.
D)
A and B might work.
E)
A, B, and C might work.
F)
None of the above will work.
A positive result for the yeast two-hybrid analysis means the following:
A)
The proteins that you are studying can be made into fusion proteins, but do NOT interact with each other within the nucleus of yeast.
B)
A fusion protein containing the Gal4p activation domain, has bound to RNA polymerase resulting increase transcription of numerous genes, including the reporter gene, and formation of colonies.
C)
Two fusion proteins, one containing the Gal4p binding site domain and one containing the Gal4p activation domain, have interacted through their Gal4p domains resulting in transcription of the reporter gene.
D)
Two fusion proteins interact with each other and because of the Gal4p binding site domain and the Gal4p activation domain contained in each fusion protein, the reporter genes are activated and the cells die resulting in no colonies.
E)
The colonies growing are expressing the two fusion proteins, but the two proteins have not interacted with each other.
Which of the following is the approximate size of the human genome?
A)
3 Gm
B)
300 Kb
C)
3 Mb
D)
3 Gb
E)
3 Mm
Which of the following is correct about the structure or location of genes?
Question 22 options:
A)
Prokaryotic genes typically possess their own regulatory sequences that only control expression of a single gene.
B)
Eukaryotic genes often encode introns that are spliced out before translation.
C)
Eukaryotic genes are mostly located at the telomeres and the centromeres of chromosomes.
D)
Eukaryotic genes are typically arranged in operons.
E)
Prokaryotic genes often encode exons that are spliced out before translation
A)
Base composition changes as the organism ages.
B)
Base composition of DNA does not vary from one species to another.
C)
In all species the number of adenines equals the number of guanines.
D)
In all species A + T = G + C.
E)
DNAs isolated from different tissues of the same species have the same base composition.
Explanation / Answer
1. C- In all species A+T=G+C
2. B- the temperature at which double-stranded DNA is too single-stranded to ever renature back to double strands.
3. E -Western blotting for the detection of specific proteins that have been separated by gel electrophoresis.
4. A- Cytidine is deaminated to uracil so it would be difficult for any repair mechanism to differentiate between uracil that belongs in the sequence and uracil that resulted from deamination.
This option is correct if there is Cytosine instead of Cytidine which is a typing error, I expect. Please check
5. B- Restriction endonuclease
6. B- Alkaline phosphatase
7. B- Reverse transcriptase
8- E All of the above are features of plasmid vectors.
9. A- Genes represented in cDNA libraries include control sequences that direct transcription.
10. C- DNA ligase to connect the fragments together
11. C- Portions of two different genes are ligated together to create a new hybrid gene. When expressed the gene product is a fusion of the two gene products.
12. D- The presence of just a few molecules of GFP fusion proteins can be sufficient for observing the proteins microscopically allowing the study of its location and movements in the cell.
13.E- A, B, and C might work.
14. C- Two fusion proteins, one containing the Gal4p binding site domain and one containing the Gal4p activation domain, have interacted through their Gal4p domains resulting in transcription of the reporter gene.
15. C- 3Mb
16. A- Prokaryotic genes typically possess their own regulatory sequences that only control expression of a single gene.
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