Select the most correct statement regarding nucleic acids.
DNA is a long, double-stranded molecule made up of A, T, G, and C bases.
tDNA is considered a "molecular slave" of DNA during protein synthesis.
Three forms exist: DNA, RNA, and tDNA.
RNA is a long, single-stranded molecule made up of the bases A, T, G, and C.
The Correct Answer is A
A. DNA is a long, double-stranded molecule made up of A, T, G, and C bases: DNA consists of two complementary strands forming a double helix. Its sequence of adenine (A), thymine (T), guanine (G), and cytosine (C) encodes genetic information for protein synthesis and inheritance.
B. tDNA is considered a "molecular slave" of DNA during protein synthesis: There is no molecule called tDNA. Transfer RNA (tRNA) carries amino acids during protein synthesis, but the term “tDNA” is incorrect and does not exist in molecular biology.
C. Three forms exist: DNA, RNA, and tDNA: Only DNA and RNA are recognized types of nucleic acids. tDNA is not a valid classification, so this statement is inaccurate.
D. RNA is a long, single-stranded molecule made up of the bases A, T, G, and C: RNA is single-stranded, but it contains uracil (U) instead of thymine (T). Its bases are adenine (A), uracil (U), guanine (G), and cytosine (C).
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. Formed elements: Formed elements include red blood cells, white blood cells, and platelets, which together make up the cellular portion of blood. These are suspended within plasma but are not considered part of plasma itself.
B. Salts: Salts such as sodium, potassium, and chloride are present in plasma as electrolytes. While they are vital for maintaining osmotic balance and nerve conduction, they make up only a small fraction of plasma’s total volume.
C. Sugars: Glucose and other sugars circulate in plasma to provide energy for cells, but their concentration is relatively low. They are important solutes but do not represent the bulk of plasma.
D. Water: Plasma is composed of about 90–92% water, making it the main component. Water serves as the solvent that carries nutrients, hormones, gases, and waste products, enabling transport and regulation within the circulatory system.
Correct Answer is D
Explanation
A. All the isotopes of the same element react differently: Isotopes generally exhibit the same chemical behavior because they have the same number of protons and electrons, which determine chemical reactivity.
B. Isotopes occur only in the heavier elements: Isotopes are found in both light and heavy elements; they are variations of an element with differing numbers of neutrons, not limited to heavy elements.
C. All the isotopes of an element have the same number of neutrons but differing numbers of electrons: Isotopes have the same number of protons (and electrons if neutral) but differ in neutron number.
D. Isotopes of the same element have the same atomic number but differ in their atomic mass (weight) number: Isotopes share the same number of protons (atomic number) but have different numbers of neutrons, which changes their mass number.
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