which of the following does not exist in rna

ATI TEAS 7

Science TEAS Practice Test

1. Which of the following nucleobases does not exist in RNA?

A. Uracil
B. Thymine
C. Cytosine
D. Guanine

Correct answer: B

Rationale: The correct answer is 'B: Thymine'. Thymine is a nucleobase found in DNA but is replaced by uracil in RNA. RNA contains Uracil, Cytosine, and Guanine as its nucleobases. Cytosine and Guanine are present in both DNA and RNA, while Thymine is exclusive to DNA and Uracil is specific to RNA.

2. What is the relationship between work and the displacement of an object?

A. Work depends only on the force applied, not displacement
B. Work is directly proportional to displacement
C. Work is inversely proportional to displacement
D. Work is unrelated to displacement

Correct answer: B

Rationale: Work is directly proportional to displacement. In physics, work is defined as the product of the force applied to an object and the displacement of the object in the direction of the force. Therefore, work is directly proportional to displacement. Choice A is incorrect because work is dependent on both force and displacement. Choice C is incorrect because work is not inversely proportional to displacement; it is directly proportional. Choice D is incorrect because work is indeed related to displacement, as described in the definition of work in physics.

3. What is the term for the gradual loss of topsoil due to wind or water erosion?

A. Desertification
B. Leaching
C. Salinization
D. Acidification

Correct answer: A

Rationale: A) Desertification is the correct term for the gradual loss of topsoil due to wind or water erosion. It refers to the process by which fertile land becomes desert, usually due to factors like drought, deforestation, or inappropriate agriculture practices. This process can lead to the degradation of land and contribute to the expansion of deserts. B) Leaching is the process in which minerals are washed out of the soil by water moving downwards through it. This is different from the loss of topsoil due to erosion. C) Salinization occurs when salt accumulates in the soil, typically as a result of irrigation in arid regions. While salinization affects soil quality, it is not specifically related to the gradual loss of topsoil due to erosion. D) Acidification refers to the decrease in soil pH, often caused by factors like acid rain or the use of acidic fertilizers. This process is distinct from the gradual loss of topsoil due to erosion.

4. What is the fatty sheath that insulates some nerve fibers and speeds up signal transmission called?

A. Myelin sheath
B. Dura mater
C. Pia mater
D. Arachnoid mater

Correct answer: A

Rationale: The correct answer is A: Myelin sheath. The myelin sheath is a fatty layer that surrounds and insulates some nerve fibers, facilitating the rapid transmission of signals along the nerve fibers. Choices B, C, and D (Dura mater, Pia mater, and Arachnoid mater) are layers of the meninges, protective membranes that surround the brain and spinal cord. The primary function of the meninges is to protect and support the central nervous system, not to insulate nerve fibers for signal transmission.

5. Which of the following describes a reflex arc?

A. The storage and recall of memory
B. The maintenance of visual and auditory acuity
C. The autoregulation of heart rate and blood pressure
D. A stimulus and response controlled by the spinal cord

Correct answer: D

Rationale: Choice D correctly describes a reflex arc. A reflex arc is a neural pathway that controls a reflex action. It involves a specific sequence of events that occur in response to a stimulus, which is rapidly and involuntarily processed by the spinal cord. The spinal cord coordinates the quick processing of sensory input and the generation of a motor response without involving the brain, allowing for rapid protective responses. Choices A, B, and C are incorrect because they do not accurately describe a reflex arc. A reflex arc is specifically related to the rapid and involuntary response to a stimulus through neural pathways involving the spinal cord, not memory storage, visual and auditory acuity maintenance, or heart rate and blood pressure autoregulation.