In this figure, the magnitude of the secondary response is due to ____________________
a. the presence of memory cells
b. the presence of antibodies that remain in the body after a first-time infection
c. the activity of killer T-cells
d. antibodies introduced when someone receives a vaccination
A
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Endospore-forming bacteria like Bacillus species begin the sporulation process with an asymmetric cell division to produce two cells with different fates. One will differentiate into the endospore, and the other is the sporangium that will ultimately lyse to release the mature endospore. (Review Process Figure 4.24.) During this asymmetric cell division, one of the compartments does not receive an intact copy of the chromosome. Which compartment can function with only part of the genome and why?
A. The endospore; it is a dormant stage and requires very little to maintain its dormancy. B. The sporangium; it supports endospore development and then lyses. C. The sporangium; much of the genome is "junk DNA" and not required for endospore maturation. D. The endospore; the endospore is built from the outside via the sporangium and not from the inside.
The expression of the lac operon in an E. coli cell missing the gene that encodes for the lac repressor:
A. will increase when lactose is present. B. will decrease when lactose is present. C. will decrease when glucose is present. D. will increase when glucose is present.
Some plants require water for reproduction. This is because
a. it is needed for germination of the spores. b. the eggs would dry out otherwise. c. the sperm are motile and need to swim to the egg to accomplish fertilization. d. the plants must be actively growing in order to reproduce. e. the seeds will be carried on the water to new sites.
Lactose transport by membrane proteins occurs under conditions in which the concentration of lactose inside the cell is higher than the concentration outside the cell. What type of transport is used to move lactose into the cell?
a. Simple diffusion b. Active transport c. Osmosis d. Facilitated diffusion