Questions and Answers
DNA is usually double-stranded, whereas RNA is usually single-stranded.
True
What are the three components of nucleotides?
A pentose sugar, a nitrogenous base, a phosphate group.
What is the difference between a deoxyribose sugar and a ribose sugar?
Deoxyribose sugar has one less oxygen molecule than ribose sugar.
Which of these nitrogenous bases is found in DNA but not in RNA?
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Which two nitrogenous bases are purines?
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Which three nitrogenous bases are pyrimidines?
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Purines are __________-ring structures, whereas pyrimidines are __________-ring structures.
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In a nucleotide, the nitrogenous base is attached to the sugar's _________ carbon and the phosphate group is attached to the sugar's ______ carbon.
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Nucleic acids are assembled in the _________ direction.
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New nucleotides are added to the ______ end of a growing polynucleotide.
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What is the role of DNA polymerase during DNA synthesis?
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A hydroxyl is present at the 3' end of the growing DNA strand. What is at the 5' end?
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What provides the energy to drive the endergonic reaction of adding a nucleotide onto a DNA strand?
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Given a template strand of 3'-ATGCTTGGACA-5' and a partially-made complementary strand containing only 5'-TAC-3', what would be the sequence of the new strand of DNA if the only additional nucleotides available to DNA polymerase were those containing the bases G, A, and C?
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DNA polymerase will continue to add nucleotides onto the growing strand as long as it has nucleotides with the bases required to complement the template strand. If it is missing one kind of base, it will stop at that point on the strand.
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What materials does DNA polymerase require in order to synthesize a complete strand of DNA? Select all that apply.
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In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.
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Short segments of newly synthesized DNA are joined into a continuous strand by _____.
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Study Notes
DNA and RNA Structures
- DNA is typically double-stranded, whereas RNA is usually single-stranded.
- Nucleotides consist of three components: a pentose sugar, a nitrogenous base, and a phosphate group.
Sugar Variants
- Deoxyribose sugar differs from ribose sugar due to one less oxygen atom; deoxyribose has two oxygen atoms, while ribose has three.
Nitrogenous Bases
- Thymine is present in DNA but absent in RNA.
- Purines include guanine (G) and adenine (A).
- Pyrimidines consist of cytosine (C), thymine (T), and uracil (U).
Structural Differences
- Purines have a double-ring structure; pyrimidines have a single-ring structure.
Nucleotide Structure
- In a nucleotide, the nitrogenous base attaches to the 1' carbon of the sugar, while the phosphate group is linked to the 5' carbon.
- Nucleic acids are synthesized in the 5' to 3' direction.
- New nucleotides are added to the 3' end of a growing polynucleotide.
DNA Polymerase Function
- DNA polymerase catalyzes the addition of nucleotides to the 3' end of a growing DNA strand.
- The 5' end of a growing DNA strand has a phosphate group, while the 3' end has a hydroxyl group.
- Energy for adding nucleotides comes from the release and hydrolysis of pyrophosphate from incoming nucleotides.
DNA Complementation
- Given a template strand 3'-ATGCTTGGACA-5' and an incomplete complementary strand 5'-TAC-3', the sequence of the completed strand would be 5'-TACGAACC-3'.
- DNA polymerase requires a single-stranded DNA template, a 3'-OH end of the new strand, and all four deoxyribonucleotides triphosphates (dATP, dCTP, dGTP, dTTP) to synthesize a complete DNA strand.
Base Pairing Rules
- In DNA, adenine pairs with thymine and guanine pairs with cytosine.
Joining of DNA Segments
- Short segments of newly synthesized DNA are joined into a continuous strand by DNA ligase (indirectly inferred).
Studying That Suits You
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Description
Test your knowledge of DNA and RNA with these flashcards from BIOL 1107K Chapter 16. This quiz covers key concepts such as the structure of nucleotides and the differences between sugars in DNA and RNA. Perfect for reinforcing your understanding of molecular biology.
