which statement most accurately compares and contrasts the structures of dna and rna

ATI TEAS 7

ATI TEAS 7 Science Practice Test

1. Which statement most accurately compares and contrasts the structures of DNA and RNA?

A. Both DNA and RNA have 4 nucleotide bases. Three of the bases are the same, but the fourth base is thymine in DNA and uracil in RNA.
B. Both DNA and RNA have the same 4 nucleotide bases. However, the nucleotides bond differently in DNA compared to RNA.
C. Both DNA and RNA have different numbers of nucleotide bases. DNA is a double helix while RNA is a single strand.
D. Both DNA and RNA have a double helix structure. However, DNA contains 6 nucleotide bases and RNA contains 4 nucleotide bases.

Correct answer: A

Rationale: The correct answer is A because DNA and RNA both consist of 4 nucleotide bases, namely adenine, cytosine, and guanine, which are common in both. The key difference lies in the fourth base, which is thymine in DNA and uracil in RNA. This distinction is fundamental in understanding the structural variances between DNA and RNA. Choice B is incorrect as it incorrectly states that the nucleotides bond differently in DNA compared to RNA without specifying the crucial base differences. Choice C is inaccurate as it misrepresents the numbers of nucleotide bases in DNA and RNA, and incorrectly describes DNA as a double helix and RNA as a single strand, which is not related to the difference in bases. Choice D is incorrect as it inaccurately portrays DNA with 6 nucleotide bases and RNA with 4, which is not true; both DNA and RNA have 4 nucleotide bases, but with differences in one of the bases.

2. Which property of a substance resists a change in its shape?

A. Density
B. Mass
C. Inertia
D. Elasticity

Correct answer: D

Rationale: Elasticity refers to a material's ability to resist deformation and return to its original shape after stress is applied. It is the property that resists a change in shape. Density is the mass per unit volume of a substance. Mass is the amount of matter in an object, while inertia is the tendency of an object to resist changes in its state of motion. Viscosity, not mentioned in the question, is the resistance of a fluid to flow, not shape change.

3. Where does mRNA translation typically occur?

A. On the ribosome
B. In the nucleus
C. In the cytoplasm
D. On the smooth endoplasmic reticulum

Correct answer: A

Rationale: mRNA translation typically occurs on the ribosome. Ribosomes are the cellular machinery responsible for protein synthesis. They read the mRNA sequence and assemble amino acids into a polypeptide chain during translation. The correct answer is A. Choices B, C, and D are incorrect. The nucleus is where mRNA is transcribed from DNA, while translation occurs in the cytoplasm on ribosomes. The smooth endoplasmic reticulum is involved in protein processing and transport but not in mRNA translation.

4. Which structure in the digestive system absorbs the most nutrients?

A. Stomach
B. Small intestine
C. Large intestine
D. Esophagus

Correct answer: B

Rationale: The small intestine is the primary site where the absorption of nutrients from digested food occurs. Its large surface area, specialized cells, and villi play key roles in maximizing nutrient absorption, making it the structure in the digestive system that absorbs the most nutrients. The stomach's main function is to break down food with acid and enzymes, not absorb nutrients. The large intestine primarily absorbs water and electrolytes, not nutrients. The esophagus is a muscular tube that connects the throat with the stomach and does not play a role in nutrient absorption.

5. During swallowing, what is the role of the epiglottis, a small flap of cartilage located near the base of the tongue?

A. Initiates the swallowing reflex
B. Grinds food into smaller pieces
C. Covers the trachea to prevent food aspiration
D. Stores saliva for lubrication

Correct answer: C

Rationale: The epiglottis plays a crucial role during swallowing by covering the trachea to prevent food or liquid from entering the airway, which could lead to aspiration. By acting as a lid over the trachea, it ensures that food passes down the esophagus to the stomach, preventing it from entering the lungs. Choice A is incorrect as the swallowing reflex is a coordinated muscular action involving the tongue and throat muscles. Choice B is incorrect as grinding food into smaller pieces is primarily the function of the teeth and the initial stages of digestion. Choice D is incorrect as the storage of saliva for lubrication is not a function of the epiglottis, but rather involves salivary glands.