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Questions and Answers
What type of DNA structure is found in prokaryotes?
What type of DNA structure is found in prokaryotes?
How many base pairs are present in each turn of the DNA helix?
How many base pairs are present in each turn of the DNA helix?
What stabilizes the DNA double helix structure?
What stabilizes the DNA double helix structure?
What is Chargaff’s rule regarding complementary bases?
What is Chargaff’s rule regarding complementary bases?
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Which structure is characterized by a left-handed helix and a zigzag shape?
Which structure is characterized by a left-handed helix and a zigzag shape?
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What is the total DNA content in a human cell as indicated by the number of chromosomes?
What is the total DNA content in a human cell as indicated by the number of chromosomes?
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Which type of DNA is considered extranuclear in eukaryotic cells?
Which type of DNA is considered extranuclear in eukaryotic cells?
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What is the primary function of histones in chromatin structure?
What is the primary function of histones in chromatin structure?
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What are the components of a nucleotide?
What are the components of a nucleotide?
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Which nitrogenous base is present in RNA but not in DNA?
Which nitrogenous base is present in RNA but not in DNA?
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What type of bond connects nucleotides to form DNA or RNA?
What type of bond connects nucleotides to form DNA or RNA?
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Which process involves the removal of an amino group from a nitrogenous base?
Which process involves the removal of an amino group from a nitrogenous base?
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What is the primary sugar component of DNA nucleotides?
What is the primary sugar component of DNA nucleotides?
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Which nucleic acid is characterized by having 3',5' phosphodiester bonds?
Which nucleic acid is characterized by having 3',5' phosphodiester bonds?
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Which of the following molecules is a high-energy source derived from nucleotides?
Which of the following molecules is a high-energy source derived from nucleotides?
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What distinguishes purine bases from pyrimidine bases?
What distinguishes purine bases from pyrimidine bases?
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Study Notes
Nucleotide Structure and Function
- Nucleotides are the building blocks of DNA and RNA.
- They are composed of a pentose sugar, a nitrogenous base, and a phosphate group.
- The sugar in DNA is deoxyribose, and in RNA it is ribose.
- Nitrogenous bases are either purines (adenine, guanine) or pyrimidines (cytosine, uracil, thymine).
- Purines form N-glycosidic bonds with C1 by N9.
- Pyrimidines form N-glycosidic bonds with C1 by N1.
- Phosphate groups attach to the sugar via phosphoester bonds.
- Removal of a phosphate group converts a nucleotide to a nucleoside.
- A nucleotide has a 5' and 3' end.
Phosphodiester Bonds
- Phosphodiester bonds connect nucleotides.
- They are covalent bonds.
- The 3' carbon of one nucleotide's sugar bonds to the 5' phosphate of the next.
- This forms the sugar-phosphate backbone of DNA or RNA.
Nucleotide Polymerization
- Nucleotides are added to a growing strand as triphosphates.
- During polymerization, the two phosphate groups are removed.
- The energy released from this process drives the reaction.
Nucleases
- Enzymes that hydrolyze phosphodiester bonds.
- Endonucleases cleave internal bonds, while exonucleases cleave at the ends.
- Excinucleases cause double cuts.
DNA Structure
- DNA is a double-stranded helix.
- The two strands are held together by hydrogen bonds between complementary bases: adenine with thymine, and guanine with cytosine.
- The base pairs are held apart by the sugar-phosphate backbone.
- The strands run antiparallel (5' to 3' on one strand, 3' to 5' on the other).
- Humans have 23 chromosome pairs.
DNA Structure (Cont.)
- Each turn of the DNA helix contains 10 base pairs.
- DNA has 3 forms: A,B, and Z-form.
- A-form is right-handed, with 11 base pairs per turn.
- B form is the standard DNA structure and is right handed with 10 base pairs per turn.
- Z form is left-handed, with 12 base pairs per turn.
DNA Secondary Structure
- Double-stranded linear (eukaryotic chromosomes)
- Double-stranded circular (mitochondria, prokaryotes, plasmids, viruses, and chloroplasts)
- Single-stranded circular (small viruses)
- The DNA is further organized within cells into chromatin.
Chromatin
- Eukaryotes package DNA by binding to histone proteins.
- This packaging forms nucleosomes.
- Nucleosomes are further organized into higher-order structures (30 nm fiber).
- Non-histone proteins further compact the structure.
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Description
Test your knowledge on the structure and function of nucleotides, the essential building blocks of DNA and RNA. This quiz covers the components of nucleotides, phosphodiester bonds, and the process of nucleotide polymerization. Prepare to explore the critical roles of these molecules in genetics!
