RNA molecules differ from DNA molecules because only RNA
does not have thymine.
has uracil.
All of the choices are correct.
is typically one strand of nucleotides (single stranded)
has ribose.
The Correct Answer is C
A. does not have thymine: DNA contains the nitrogenous base thymine, whereas RNA lacks thymine. Instead, RNA uses uracil in place of thymine during base pairing. Because thymine is absent from RNA molecules, this difference is one of the key biochemical distinctions between RNA and DNA structure.
B. has uracil: RNA contains the nitrogenous base uracil, which pairs with adenine during RNA synthesis and function. In DNA, thymine performs this role instead. The substitution of uracil for thymine is a defining molecular feature that distinguishes RNA nucleotides from DNA nucleotides.
C. All of the choices are correct: Each of the listed statements accurately describes a property unique to RNA compared with DNA. RNA lacks thymine, contains uracil, typically exists as a single-stranded molecule, and contains ribose sugar rather than deoxyribose. Because every option describes a valid structural difference, this is the most accurate answer.
D. is typically one strand of nucleotides (single stranded): RNA molecules are generally single-stranded, allowing them to fold into complex secondary and tertiary structures that support functions such as translation and gene regulation. DNA, in contrast, usually exists as a double-stranded helix with complementary base pairing between strands.
E. has ribose: RNA nucleotides contain ribose sugar, which includes a hydroxyl group on the 2′ carbon of the pentose ring. DNA contains deoxyribose, which lacks this oxygen atom. This chemical difference contributes to RNA being more reactive and less stable than DNA.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. Halophile: Halophiles are organisms that thrive in high-salt environments. The description of temperature-based growth does not indicate a preference for saline conditions, so this term would not apply to the observed growth pattern.
B. Anaerobe: Anaerobes are organisms that grow in the absence of oxygen. The scenario focuses on temperature preferences, not oxygen requirements.
C. Mesophile: Mesophiles grow optimally at moderate temperatures, typically between 20°C and 45°C, with 37°C being ideal for many human-associated mesophilic bacteria. Because this species did not grow at 37°C or 50°C, it does not fit the definition of a mesophile.
D. Psychrophile: Psychrophiles are organisms that thrive at cold temperatures, usually with optimal growth at 0–15°C and survival at temperatures below 20°C. The abundant growth in the refrigerator and minimal growth at room temperature, with no growth at 37°C or higher, indicates that this species is adapted to cold environments, fitting a psychrophile definition.
E. Capnophile: Capnophiles require elevated levels of carbon dioxide for optimal growth. The growth pattern described is based on temperature rather than carbon dioxide levels, so this term is not applicable.
Correct Answer is A
Explanation
A. Obligate aerobe: An obligate aerobe requires oxygen for growth because it relies on aerobic respiration to produce ATP. Without oxygen, these bacteria cannot generate sufficient energy and will fail to survive. Examples include Mycobacterium tuberculosis and Pseudomonas aeruginosa.
B. Obligate anaerobe: An obligate anaerobe cannot tolerate oxygen and may be killed or inhibited by its presence. These bacteria rely on fermentation or anaerobic respiration for energy and are typically found in oxygen-free environments such as deep tissues or the gastrointestinal tract.
C. Aerotolerant organism: Aerotolerant organisms do not require oxygen for growth but can survive in its presence. They rely on fermentation exclusively and are indifferent to oxygen, unlike obligate aerobes which must have it for survival.
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