#Question id: 2870
#Unit 2. Cellular Organization
In Escherichia coli, the synthesis of tryptophan is controlled by the tryptophan operon that is repressed in the presence of excessive tryptophan. When a mutant strain that has lost the regulatory gene of the tryptophan operon is placed in a medium that contains all nutrients the cells need to grow except tryptophan, which of the following will occur?
#Question id: 2871
#Unit 2. Cellular Organization
With respect to X-chromosome inactivation in females, which, if any, of the following statements is incorrect?
#Question id: 2872
#Unit 2. Cellular Organization
Concerning disorders resulting from unstable expansion of tandem oligonucleotide repeats, which, if any of the following statements is false.
A) The expansions can occur in coding DNA in some cases, and in noncoding DNA in other cases.
B) The repeats are of a variable number of nucleotides (from three to six) in both coding DNA and noncoding DNA.
C) The expansions in noncoding DNA are generally much larger in size than those in coding DNA.
D) The expanded arrays in noncoding DNA always result in loss of function of the host gene or of a neighboring gene.
#Question id: 2873
#Unit 2. Cellular Organization
With reference to aberrant methylation of bases which of the following statements, if any, is false?
#Question id: 2874
#Unit 2. Cellular Organization
Match one item from numbered group A with a lettered item from group B.
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GROUP I |
GROUP II |
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1. Yeast artificial chromosomes |
a. They are more stable |
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2. Bacterial artificial chromosome |
b. It is very hard to construct |
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c. It is not so hard to construct |
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d. They are unstable |
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e. are used to clone the DNA inserts up to 300kb |
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f. are used for cloning very large (1000-2000kb) DNA segments |
#Question id: 2875
#Unit 2. Cellular Organization
Which of the following statements is/are CORRECT from the following?
I. The chromosome of the small monkey DNA virus SV40 is a circular, double-helical DNA molecule of 5000 bp.
II. The phage Lambda genome is a linear single-stranded molecule in the virion particle.
III. Circular DNA molecules purified from both bacteria and eukaryotes are usually negatively supercoiled, having values of sigma of approximately –0.06.
IV. Prokaryotes have a special type I topoisomerase known as “DNA gyrase” that introduces, rather than removes, negative supercoils.
V. DNA disentanglement, generally catalyzed by a type II topoisomerase, is also required for a successful round of DNA replication and cell division in eukaryotes.