In a mutant E. coli strain, there was a mutation in the malate dehydrogenase gene that resulted in a stop codon at amino acid position 14. From subcultures of this strain, a colony was obtained that was capable of making malate dehydrogenase. Your approach to examining this phenomenon should be to examine
A) the DNA sequence to see if a reversion has occurred.
B) the DNA sequence to see if a suppresor mutation has occurred.
C) other proteins to see if other stop codons are ignored, indicating the presence of a suppresor tRNA.
D) the DNA and plasmids for the incorporation of a second complete copy of the malate dehydrogenase gene.
E) all of the above
E) all of the above
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Scientists have found that the lifetimes of mRNAs coding for pair-rule regulatory elements in Drosophila embryos may last only a few minutes. What does this suggest about the overall developmental plan of an animal body?
A) The role of mRNAs is less important than the position of genes in chromosomes. B) Homeotic genes have greater impact in forming an embryo than mRNA from pair-rule genes. C) Building an animal body requires a sequence of precisely timed steps. D) Timing of pair-rule sequence determination is not as important as spatial signaling.
Over twisting or under twisting of helical DNA generates
A. hypertwists. B. hypercoils. C. supercoils. D. hypotwists.
Antiviral drugs are often difficult to develop, largely because
A. viruses are more abundant in the body than bacterial cells. B. viruses are obligate intracellular parasites so the drugs must enter the host cell and often cause toxic side effects in order to destroy the virus. C. viruses are more pathogenic than bacterial cells. D. viruses are much smaller than bacterial cells.
The individual generally credited with the discovery of cells is:
A) Robert Hooke B) Matthias Schleiden C) Rudolph Virchow D) Peter the Great E) Anton van Leeuwenhoek