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Questions and Answers
What role does methylated cytosine typically play in gene expression?
What role does methylated cytosine typically play in gene expression?
- It enhances gene expression.
- It promotes DNA replication.
- It represses gene expression. (correct)
- It has no effect on gene expression.
How are hypoxanthine and xanthine related to purine metabolism?
How are hypoxanthine and xanthine related to purine metabolism?
- They are bases added to nucleotides.
- They are intermediates in the catabolism of purines. (correct)
- They directly enhance nucleotide activity.
- They are products of purine synthesis.
What distinguishes a nucleotide from a nucleoside?
What distinguishes a nucleotide from a nucleoside?
- A nucleotide contains only nitrogen bases.
- Nucleotides contain sulfur groups.
- A nucleotide has a phosphate group attached. (correct)
- Nucleosides are nucleotides without ribose.
Which of the following is a methylated purine found in coffee?
Which of the following is a methylated purine found in coffee?
What modification occurs to the name of purines when forming nucleosides?
What modification occurs to the name of purines when forming nucleosides?
What type of sugar is found in RNA nucleotides?
What type of sugar is found in RNA nucleotides?
Which of the following nitrogen bases is categorized as a purine?
Which of the following nitrogen bases is categorized as a purine?
Which modified base is commonly found in DNA?
Which modified base is commonly found in DNA?
How are the carbon atoms in the sugar of nucleotides numbered?
How are the carbon atoms in the sugar of nucleotides numbered?
Which nitrogen base is not found in DNA?
Which nitrogen base is not found in DNA?
What is the primary role of nucleic acids?
What is the primary role of nucleic acids?
How are nucleotides named?
How are nucleotides named?
Which base pairing rule correctly describes the pairing in DNA?
Which base pairing rule correctly describes the pairing in DNA?
What type of linkage forms between nucleotides in nucleic acids?
What type of linkage forms between nucleotides in nucleic acids?
In which conformation do nucleosides typically adopt in the DNA duplex?
In which conformation do nucleosides typically adopt in the DNA duplex?
What distinguishes deoxyribonucleic acid (DNA) from ribonucleic acid (RNA) at the sugar level?
What distinguishes deoxyribonucleic acid (DNA) from ribonucleic acid (RNA) at the sugar level?
What is the significance of the absorption of UV light at 260nm by nucleotides?
What is the significance of the absorption of UV light at 260nm by nucleotides?
Which modified base is typically associated with RNA?
Which modified base is typically associated with RNA?
What unique property of nucleotides facilitates their movement in gel electrophoresis?
What unique property of nucleotides facilitates their movement in gel electrophoresis?
Which nucleoside is an exception by adopting the syn conformation?
Which nucleoside is an exception by adopting the syn conformation?
What characteristic shape does Z DNA primarily exhibit?
What characteristic shape does Z DNA primarily exhibit?
Which properties allow nucleotides to be distinguished during DNA quantification?
Which properties allow nucleotides to be distinguished during DNA quantification?
What can be inferred about the conformations of purines and pyrimidines in Z DNA?
What can be inferred about the conformations of purines and pyrimidines in Z DNA?
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Study Notes
Nucleic Acids Overview
- Nucleic acids store information essential for cellular growth and reproduction.
- Two primary types: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
- Composed of long chains of monomers called nucleotides.
Nucleotide Structure
- A nucleotide consists of:
- A pentose sugar: ribose in RNA (OH at the 2' carbon) and deoxyribose in DNA (H at the 2' carbon).
- A nitrogen base (either purine or pyrimidine).
- A phosphate group.
- Sugar carbon atoms are numbered as 1’, 2’, 3’, 4’, and 5’ to differentiate them from nitrogen bases.
Nitrogen Bases
- Nitrogen bases are planar, allowing for stacking.
- Types of nitrogen bases:
- Purines (bicyclic): Adenine (A) and Guanine (G).
- Pyrimidines (monocyclic): Cytosine (C), Thymine (T), and Uracil (U).
Modified Bases
- Nucleic acids can include unusual or modified bases in smaller quantities:
- Examples:
- 5-methyl cytosine (DNA)
- N6-methyl adenine (DNA)
- Pseudouracil (RNA)
- Examples:
- Functions of modified bases:
- Important for oligonucleotide recognition.
- Methylated cytosine in promoter regions influences gene expression.
- Methylated purines in plants are linked to caffeine and related compounds.
Nucleosides and Nucleotides
- A nucleoside is a nitrogen base linked to a sugar (ribose or deoxyribose) via a glycosidic bond.
- Named with -osine (purines) and -idine (pyrimidines).
- A nucleotide is a nucleoside with a phosphate group attached.
- Named using the nucleoside name followed by 5’-monophosphate.
Conformation of Nucleotides
- Nucleosides in DNA primarily adopt the anti conformation.
- Guanosine monophosphate can adopt a syn conformation.
- Z DNA exhibits purines in syn conformation and pyrimidines in anti conformation, creating a zig-zag shape.
Properties of Nucleotides
- Nucleotides absorb UV light at 260 nm due to cyclic nitrogen bases, allowing quantification and purity checks of DNA.
- Nucleotides possess a negative charge due to the phosphate group, utilized in gel electrophoresis for nucleic acids.
Summary
- Nucleic acids are crucial for genetic information storage and expression, with nucleotides as their building blocks.
- Various types of nitrogen bases and modifications play key roles in the functionality of nucleic acids, influencing biological processes dramatically.
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