Down syndrome is due to an extra

A. X chromosome.
B. autosome.
C. Y chromosome.
D. X chromosome or an extra Y chromosome.


Answer: B

Anatomy & Physiology

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When an impulse arrives at the knob of the motor neuron, calcium

A. enters through active transport pumps and triggers the release of transmitter. B. enters through voltage-gated channels and triggers the release of transmitter. C. is released from synaptic vesicles. D. exits through voltage-gated channels and triggers transmitter release. E. exits through active transport pumps and brings transmitter with it.

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Which type of cell makes up about 90% of the alveolar surface?

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Anatomy & Physiology