#Question id: 2954
#Unit 2. Cellular Organization
Cyclin concentrations are highest during which periods of the cell cycle?
#Question id: 12348
#Unit 10. Ecological Principles
#Question id: 16953
#Unit 4. Cell Communication and Cell Signaling
#Question id: 2585
#Unit 2. Cellular Organization
Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fiber?
A. Tropomyosin shifts and unblocks the cross-bridge binding sites.
B. Calcium is released and binds to the troponin complex.
C. Transverse tubules depolarize the sarcoplasmic reticulum.
D. The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP.
E. An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane.
#Question id: 2810
#Unit 2. Cellular Organization
Which of the following steps is required to generate a knockout mouse?
a. microinjection of DNA into the pronucleus of a fertilized mouse egg
b. introduction of DNA into mouse embryonic stem cells
c. selection for cells containing the gene targeted insertion
d. expression of Cre protein during embryonic development