Bacteria are grown in 15N (heavy) medium and then transferred to 14N (light) medium and are allowed to replicate for 1 generation. The DNA is subsequently isolated and centrifuged in a CsCl2 gradient to yield what type of gradient band(s)?
A. one heavy band.
B. one light band.
C. one half-heavy (intermediate to heavy and light) band.
D. one heavy and one half-heavy band.
E. one heavy and one light band.
C. one half-heavy (intermediate to heavy and light) band.
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Both pocket mice and peppered moths are exposed to selection pressure caused by ________
a. industrial pollution b. predators c. temperature changes in their habitats d. vegetative disruptions caused by introduced plant species
While a locus refers to a unit of heredity, a gene refers to a specific position on a chromosome.
Answer the following statement true (T) or false (F)
Phenetics is based upon straightforward comparison of the measurements of the traits of specimens (or on a comparison of their head-length-to-width-ratios, for instance, in order to compensate for juveniles, etc.). However, which of the following situations give(s) an additional problem to this strict classification-by-similarity approach?
A. Sexual dimorphism, or differences between males and females, may lead to them being classified as different species. B. Ants and termites have many castes, from winged reproductives to smaller workers to large-jawed soldiers, all of which would appear as vastly different species. C. Organisms with different lineages may share a large number of traits if they are adapted to the same environment-a case of convergent evolution. D. The selection of traits to measure is still dependent upon what the scientist perceives as differences, and a new microscope or DNA technique would add a new set of ''objective'' traits to compare. E. All of these situations are problematic.
The onset of puberty is triggered by maturation of the brain, which stimulates the hypothalamus to secrete
A) testosterone. B) progesterone. C) gonadotropin-releasing hormone (GnRH). D) luteinizing hormone (LH). E) chorionic gonadotropin (CG).