Which stage of development results in an early embryo with two or three germ layers?
a. fertilization
b. organ formation
c. cleavage
d. gastrulation
d
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Hemoglobin transports oxygen in the blood and consists of a chain of 146 amino acids. How many different types of amino acids are used to construct proteins?
A. 2 B. 20 C. 146 D. 200
What would need to change to allow sodium and potassium ions to easily diffuse through plasma membranes?
A. They would have to shrink in size. B. The low solubility that they have in lipids would have to increase. C. The high solubility that they have in lipids would have to decrease. D. The high solubility that they have in water would have to decrease. E. The low solubility that they have in lipids would have to increase, and the high solubility that they have in water would have to decrease.
Which of the following organisms is part of the normal flora of the skin, nose, throat, and intestines of humans, and is also a leading cause of bacterial disease?
a. Propionibacterium acnes b. Corynebacterium diphtheriae c. Staphylococcus aureus d. Staphylococcus epidermidis
In Escherichia coli, when the lac operon is fully induced (in the presence of lactose):
A. lactose cannot be cleaved to enter glycolysis. B. the lac repressor is active and transcription of the lac operon does not occur. C. lactose cannot be transported by the cells. D. the lac repressor is inactive and transcription of the lac operon does occur.