The _____ is an opaque disk with an adjustable aperture that by adjusting may improve the contrast of the image.
A. Condenser
B. Objective
C. Iris diaphragm
D. Ocular
Ans: C. Iris diaphragm
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Which of the following occurs first during an action
potential? a. Many sodium ions flow into the neuron. b. Voltage-gated sodium channels open. c. A local disturbance triggers the resting voltage to reach the threshold level. d. The interior of the neuron becomes positive. e. The interior of the neuron becomes negative.
Beadle and Tatum began their studies with wild-type Neurospora, which is:
a. Neurospora that only grows in the wild. b. a mutant strain that will only grow in the lab on complete medium. c. a strain that will not grow in the lab. d. a virulent strain of Neurospora. e. a normal phenotype that will grow on minimal medium.
The chromosomes are aligned midway between spindle poles during _______________.
A. anaphase B. metaphase C. interphase D. prophase E. telophase
You are given two true-breeding strains of hamster. One strain has white fur color and the other has a dark brown fur color. When you cross the white-fur strain to the dark-brown-fur strain, you obtain F1 progeny that have a light brown fur color
When you cross the F1 progeny with each other, 25% of the F2 generation have white fur, 25% have dark brown fur, and 50% have light brown fur. How many genes crucial for fur coloration differ between the two starting strains? Explain your answer. Extra credit: Propose a molecular mechanism for how fur color is determined in this species of hamster.