A microbial geneticist observes that a significant number of pyrimidine dimers are present in bacterial DNA following exposure to a particular mutagen. To which mutagen were the bacterial cells likely exposed?

A. UV light
B. Acridine orange
C. X-rays
D. 5-bromouracil


Answer: A

Biology & Microbiology

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The last common ancestor of all bilaterians is thought to have had four Hox genes. Most extant cnidarians have two Hox genes, except Nematostella (of ?-catenin fame), which has three Hox genes. On the basis of these observations, some have proposed that the ancestral cnidarians were originally bilateral and, in stages, lost Hox genes from their genomes. If true, this would mean that _____.

A) the Radiata should be a true clade B) the radial symmetry of extant cnidarians is secondarily derived, rather than being an ancestral trait C) Hox genes play little actual role in coding for an animal's "body plan" D) the Cnidaria may someday replace porifera as the basal bilaterians B) the radial symmetry of extant cnidarians is secondarily derived, rather than being an ancestral

Biology & Microbiology

Porins are channels in the outer membranes of gram-positive Bacteria

Indicate whether the statement is true or false.

Biology & Microbiology

Unlike members of the Bacteria, most archaeons have linear chromosomes with multiple origins of replication.

Answer the following statement true (T) or false (F)

Biology & Microbiology

True or false: the genotype of a fetus can be screened for SNPs associated with some diseases

A. true B. false

Biology & Microbiology