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Questions and Answers
What type of bond is formed between the phosphate group and the sugar in a nucleotide?
Which two bases belong to the purine category in DNA?
Which component of a nucleotide is NEVER found in proteins?
What characterizes the ribose sugar found in nucleic acids?
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What is a significant difference between DNA and RNA regarding nitrogenous bases?
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Which components make up a nucleotide?
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Which of the following nitrogenous bases is found only in RNA?
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What distinguishes DNA from RNA at the molecular level?
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What is a nucleoside composed of?
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Which of the following statements is true regarding the bases in nucleic acids?
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What does Chargaff’s rule state about the relationship between adenine and thymine in DNA?
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What was one of the main conclusions from Chargaff's research on DNA?
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How did X-ray diffraction contribute to our understanding of DNA structure?
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What did Rosalind Franklin achieve in the study of DNA using X-ray diffraction?
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Which statement is true regarding the relationship between guanine and cytosine in DNA?
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What shape of molecule did the X-ray diffraction patterns suggest DNA had?
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What does Chargaff's second rule indicate?
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What did Watson and Crick contribute to the understanding of DNA?
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What did the X-ray diffraction reveal about the dimensions of the DNA helix?
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What is indicated by Chargaff's first rule?
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Both DNA and RNA contain the nitrogenous base U.
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A nucleotide consists of a nitrogenous base, a ribose sugar, and a phosphate group.
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The absence of a hydroxyl group at the C-2' position is a characteristic that distinguishes DNA from RNA.
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The purines found in nucleic acids are adenine, guanine, cytosine, and thymine.
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A nucleoside is formed when a nitrogenous base is bonded to a pentose sugar.
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DNA is primarily composed of four different types of nucleotides.
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In nucleic acids, ribose sugar is a six-membered ring structure.
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Sulfur is a component found in all amino acids but not in DNA.
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Phosphodiester bonds connect the nitrogenous bases with the sugar in a nucleotide.
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RNA contains thymine in place of uracil.
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Study Notes
Nucleic Acids: Building Blocks
- DNA & RNA are built from nucleotides
- Nucleotides have three components:
- Nitrogenous base: Adenine (A), Guanine (G), Cytosine (C), Thymine (T) (in DNA), Uracil (U) (in RNA).
- Pentose sugar: Ribose (in RNA), Deoxyribose (in DNA).
- Phosphate group
- Two types of nitrogenous bases:
- Purines: Double-ringed structures, including Adenine (A) and Guanine (G)
- Pyrimidines: Single-ringed structures, including Cytosine (C), Thymine (T), and Uracil (U).
DNA Structure
- DNA is made of four nucleotides: A, T, C, and G
- RNA contains uracil (U) instead of thymine (T)
- DNA is a double helix:
- Two strands wrap around a central axis.
- Strands are antiparallel: One strand runs 5' to 3', the other 3' to 5'.
- Phosphodiester backbone: Repeating sugar-phosphate units linked by phosphodiester bonds.
- Nitrogenous bases: Extend towards the interior of the helix, forming base pairs.
Base Complementarity
- Adenine (A) forms two hydrogen bonds with Thymine (T).
- Guanine (G) forms three hydrogen bonds with Cytosine (C).
- This pairing is called complementarity.
- The diameter of the double helix is constant due to pairing a purine with a pyrimidine.
Chargaff's Rules
- The amount of adenine (A) in DNA always equals the amount of thymine (T).
- The amount of guanine (G) always equals the amount of cytosine (C).
- A = T and G = C
- The ratio of G-C to A-T varies among different species.
Watson-Crick Model
- Two antiparallel polynucleotide chains coiled around a central axis.
- Bases of each chain are perpendicular to the axis.
- Complementary base-pairing holds strands together.
- Each turn of the helix is 3.4 nm long, containing 10 base pairs.
- Major and minor grooves alternate along the length of the molecule.
- Diameter of the double helix is 2 nm.
RNA Structure
- Similar to DNA, but with key differences:
- Ribose replaces deoxyribose.
- Uracil replaces thymine.
- Most RNA is single-stranded.
- Three classes of RNA involved in gene expression:
- Ribosomal RNA (rRNA)
- Messenger RNA (mRNA)
- Transfer RNA (tRNA)
- Uracil pairs with adenine during transcription and RNA base pairing.
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Description
This quiz covers the building blocks of nucleic acids, focusing on the structure of DNA and RNA. Learn about nucleotides, nitrogenous bases, and the unique features of double-stranded DNA, including its antiparallel strands and phosphodiester backbone.
