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IB Biology A1.2: Nucleic Acids — Practice Questions & Answers
IB Biology A1.2 Nucleic acids study notes: DNA and RNA structure, nucleotides, base pairing, antiparallel strands, and how a sequence stores information.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
What is the primary function of nucleic acids?
Storing hereditary information
Providing structural support
Catalyzing reactions
Storing energy
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Why Nucleic acids such as DNA store and transmit hereditary information between generations.
2
Multiple choice
What is the genetic material in most living organisms?
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Why DNA is the genetic material carrying inherited instructions in the vast majority of organisms.
3
Multiple choice
Which of the following is NOT considered a living organism?
Viruses
Bacteria
Plants
Animals
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Why Viruses lack cells and independent metabolism, so they are not usually classed as living organisms.
4
Multiple choice
What are the three components of a nucleotide?
Phosphate, pentose sugar, nitrogenous base
DNA, RNA, tRNA
Histones, nucleosomes, DNA
Nitrogenous backbone, pentose sugar, phosphate base
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Why Every nucleotide is built from a phosphate group, a pentose sugar and a nitrogenous base.
5
Multiple choice
In a nucleotide diagram, what shape represents the pentose sugar?
Pentagon
Circle
Rectangle
Triangle
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Why The five-carbon pentose sugar is conventionally drawn as a pentagon in nucleotide diagrams.
6
Multiple choice
What type of bond forms the sugar-phosphate backbone of DNA and RNA?
Covalent bond
Hydrogen bond
Ionic bond
Van der Waals force
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Why Strong covalent phosphodiester bonds link the sugars and phosphates that make up the nucleic acid backbone.
7
Multiple choice
What connects the nucleotides in a single strand of DNA or RNA?
Sugar-phosphate bonds
Hydrogen bonds
Peptide bonds
Glycosidic bonds
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Why Nucleotides within one strand are joined through covalent sugar-phosphate (phosphodiester) bonds.
8
Multiple choice
Which nitrogenous base is unique to DNA?
Thymine
Uracil
Cytosine
Guanine
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Why Thymine occurs only in DNA, whereas RNA uses uracil in its place.
9
Multiple choice
What is RNA formed from?
Nucleotide monomers
Amino acid monomers
Glucose monomers
Fatty acid monomers
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Why RNA is a polymer assembled from repeating nucleotide monomers.
10
Multiple choice
What type of bond links the two strands of DNA?
Hydrogen bonds
Covalent bonds
Ionic bonds
Peptide bonds
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Why The two DNA strands are held together by hydrogen bonds between complementary bases.
Key terms in Nucleic Acids
Nucleotide: The monomer of a nucleic acid, made of a pentose sugar, a phosphate group and a nitrogenous base.
Sugar–phosphate backbone: The repeating chain of alternating sugars and phosphates that forms the structural framework of a nucleic acid strand.
Complementary base pairing: The rule that A pairs with T (or U in RNA) and G pairs with C, joined by hydrogen bonds.
Purine: A double-ring nitrogenous base; adenine and guanine.
Pyrimidine: A single-ring nitrogenous base; cytosine, thymine and uracil.
Double helix: The two-stranded, spiral structure of DNA held together by hydrogen bonds between paired bases.
Antiparallel: Describing the two DNA strands running in opposite directions (one 5′→3′, the other 3′→5′).
Deoxyribose: The pentose sugar found in DNA; ribose (in RNA) has one additional oxygen atom.
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