Based on current knowledge about the conditions of early Earth, the first organisms were most likely
A) anaerobic eukaryotes.
B) photosynthetic eukaryotes.
C) anaerobic prokaryotes.
D) photosynthetic prokaryotes.
E) multicellular eukaryotes.
C
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Very high solar energy input; temperature and moisture not limiting; high biomass, high total productivity; many species.
A. desert B. savanna C. taiga D. temperate grassland E. tropical rain forest
In the Sanger method of DNA sequencing, incorporation of the nucleotides stops because
A) the dideoxynucleotide analogs have no 3'-OH group to continue DNA synthesis. B) the dideoxynucleotide analogs have no 5'-OH group to continue DNA synthesis. C) the dideoxynucleotide analogs have no 2'-OH group to continue DNA synthesis. D) the mixture is heated to 92°C to stop DNA synthesis at specific time intervals. E) the dideoxynucleotide analogs are in greater concentration than the actual nucleotides.
Which of the following statements is not true regarding Clostridium difficile?
A. Infection is precipitated by broad-spectrum antibiotic therapy. B. It produces "rice-water" stools. C. It is a gram-positive, endospore-forming rod. D. It is part of the normal intestinal biota. E. It is also called pseudomembranous colitis.
In positional cloning, the researcher begins with a phenotype. To move toward identification of its DNA sequence, she must begin with what step?
What will be an ideal response?