QUESTION: 49 Exam Topic: 1, Biology

Experiments by Thomas Hunt Morgan with the eye coloration of fruit flies demonstrated that

mutations in DNA can knock out the function of certain genes
one gene carries the code for a single protein
the genes for certain traits are carried on the X-chromosome
eye coloration genes are found on the same chromosome as genes for wing shape and length
only male fruit flies express recessive white eye coloration, while both males and females express the dominant red eye coloration

Answer(s): C

Explanation:

Morgan was the first scientist to show that certain genes were linked to the sex of an organism. These sex-linked traits were coded for by genes carried on the X-chromosome and, if recessive (such as fruit fly white eye coloration), were far more commonly expressed in males (because they have only one X chromosome) than in females. However, rare females did have white eyes in his experiments

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QUESTION: 50 Exam Topic: 1, Biology

A lack of which of the following substances would likely lead to dizziness, fatigue, and confusion due to red blood cells being less able to carry oxygen?

Calcium
Vitamin D
Zinc
Magnesium
Iron

Answer(s): E

Explanation:

Iron is the element that is a key part of hemoglobin protein in red blood cells. Iron binds to oxygen in the lungs and allows red blood cells to carry this oxygen to body cells. Without iron, insufficient oxygen reaches cells of the body. Without oxygen, cells cannot produce adequate ATP, and symptoms such as those described can occur.

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QUESTION: 51 Exam Topic: 1, Biology

The toad Bufo marinus generally lies in wait for prey such as cockroaches to wander past. As the cockroach enters the toad's field of view, the toad strikes with its sticky tongue. Yet, the cockroach begins its escape from the toad even before the tongue has left the toad's mouth, even though it may still be caught. Attacks generally occur at night and the tongue makes no detectable sound at all. Cockroaches have also seen climbing on the backs of sedentary toads.

These observations suggest that

cockroaches are repelled by the odor of a toad
cockroaches begin to flee at the sight of a toad
cockroaches can detect slight changes in wind direction
toads produce a high frequency sound detectable by the cockroach at the time of attack
the cockroach is responding to a previously misdirected attack

Answer(s): C

Explanation:

It the toads make no sound upon attack, attacks occur at night, and roaches climb on the backs of sitting toads, these observations suggests that roaches are not warned by any auditory, olfactory, or visual cues. However, as the frog opens its mouth and tenses its muscles, the wind nearby would change direction suddenly. This is picked up by the sensitive hairs on the underside and tail end of roaches, which quickly move to escape.

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QUESTION: 52 Exam Topic: 1, Biology

The data below show the response of a neuron on the skin surface to repeated stimulation with varying degrees of pressure.

Which of the following conclusions concerning the pressure-sensitive neurons of the skin can be drawn from this data?

The neurons fatigue quickly after repeated stimulation.
There is a prolonged period of depolarization that leaves the neurons refractory for as long as one second after each firing.
Increasing pressure results in an increase in amplitude of the action potential.
The neurons signal increased pressure by increasing the frequency of signals sent per unit time.
The neurons fire only after a certain pressure threshold is reached.

Answer(s): D

Explanation:

Neurons respond to stimulation in an all-or-none manner, and they do not show an increased response when presented with a greater stimulus. Rather, they signal the intensity of a stimulus by increasing or decreasing the frequency of action potentials that are generated, not by changing the amplitude (degree) of each action potential.

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QUESTION: 49 Exam Topic: 1, Biology

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QUESTION: 52 Exam Topic: 1, Biology

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