what is the structure of dna

ATI TEAS 7

ATI TEAS Science Practice Test

1. What is the structure of DNA?

A. Single-stranded, linear
B. Double-stranded, linear
C. Double-stranded, helix
D. Single-stranded, helix

Correct answer: C

Rationale: The correct answer is C: Double-stranded, helix. DNA is structured as a double helix formed by two strands of nucleotides. The nucleotides are paired with complementary bases (A-T and C-G) in the center, held together by hydrogen bonds. This double-stranded helical structure is a fundamental characteristic of DNA and essential for its function in storing genetic information. Choices A, B, and D are incorrect because DNA is not single-stranded; it consists of two strands that run antiparallel to each other and are connected via hydrogen bonds. Additionally, DNA does not have a linear structure but rather a helical one, providing stability and protection to the genetic information it carries.

2. Which of the following is an example of a long bone in the human body?

A. Carpals
B. Femur
C. Tarsals
D. Metacarpals

Correct answer: B

Rationale: The correct answer is B, Femur. The femur is the longest and strongest bone in the human body, located in the thigh region. Long bones are characterized by their elongated shape, such as the femur, which provides support, strength, and mobility. Choices A, C, and D are incorrect because carpal bones (A) are short bones found in the wrist, tarsal bones (C) are short bones found in the ankle, and metacarpal bones (D) are classified as long bones, but they are shorter than the femur and mainly found in the hand.

3. What is the role of RNA in the regulation of gene expression?

A. Provides energy for the process
B. Controls the timing and location of protein synthesis
C. Translates the genetic code into amino acids
D. Stores genetic information

Correct answer: B

Rationale: A) RNA does not provide energy for the process of gene expression. Energy is typically provided by molecules like ATP. B) RNA plays a crucial role in controlling the timing and location of protein synthesis through processes like transcriptional regulation, RNA splicing, and post-transcriptional modifications. It helps determine when and where specific proteins are produced in the cell. C) While mRNA translates the genetic code into amino acids during the process of translation, this is not the primary role of RNA in the regulation of gene expression. D) RNA does not store genetic information in the same way that DNA does. DNA is the molecule responsible for storing genetic information in the form of genes. Therefore, option B is the most appropriate choice as it accurately describes the role of RNA in regulating gene expression.

4. How is homeostasis defined?

A. The ability of human beings to keep body weight within normal limits.
B. The maintenance of a constant external temperature inside a room.
C. The ingestion of enough food to prevent hunger pains.
D. The tendency of the body to maintain a stable internal environment.

Correct answer: D

Rationale: Homeostasis is defined as the tendency of the body to maintain a stable internal environment despite external changes. This process involves regulating various physiological parameters such as body temperature, blood pressure, and glucose levels to ensure optimal functioning and health. Option A is incorrect as it specifically refers to body weight regulation, which is not the sole focus of homeostasis. Option B is incorrect as it describes maintaining a constant temperature in a room, rather than the internal environment of the body. Option C is incorrect as it only addresses the prevention of hunger pains through food ingestion, which is not the overarching concept of homeostasis.

5. What is the term for the process of exchanging gases (oxygen and carbon dioxide) between the blood and the tissues?

A. Inhalation
B. Exhalation
C. External respiration
D. Internal respiration

Correct answer: C

Rationale: External respiration is the correct term for the process of exchanging gases (oxygen and carbon dioxide) between the blood and the tissues. It specifically refers to the exchange of gases that occurs in the lungs, where oxygen is absorbed into the bloodstream and carbon dioxide is released from the bloodstream to be exhaled. Inhalation and exhalation, choices A and B, are phases of the breathing process that involve the intake and expulsion of air into and out of the lungs, respectively. Internal respiration, choice D, is the process of gas exchange that happens at the cellular level between the blood and body tissues, not between the blood and the lungs or tissues as in external respiration. Therefore, external respiration is the most appropriate term for the described gas exchange process in the question.