Nucleic Acids Overview

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Questions and Answers

What is the primary function of methylated cytosine in the promoter region of organisms?

Enhancing gene expression

Altering mRNA structure

Repressing gene expression (correct)

Promoting transcriptional activation

What are hypoxanthine and xanthine primarily considered in purine metabolism?

End products of nucleotide synthesis

Intermediates in the catabolism of purines (correct)

Precursor molecules for DNA synthesis

Secondary messengers in signal transduction

How are nucleosides named for purines and pyrimidines?

By adding -ine for purines and -ine for pyrimidines

By adding -ine for pyrimidines and -osine for purines

By using the base name followed by -osine for purines and -idine for pyrimidines (correct)

By appending -base for all types of nucleosides

Which of the following correctly describes a nucleotide?

A nucleoside with a phosphate group attached Signup and view all the answers

Which of the following methylated bases is associated with cocoa?

Theobromine Signup and view all the answers

How do nucleotides derive their name?

From the nucleoside followed by 5'-monophosphate Signup and view all the answers

In what conformation do nucleosides typically adopt in a DNA duplex?

Anti conformation Signup and view all the answers

Which nucleotide can adopt the syn conformation about the glycosidic bond?

Guanosine monophosphate Signup and view all the answers

What significant property do nucleotides possess related to UV light?

They absorb UV light at 260 nm Signup and view all the answers

What causes nucleotides to have a negative charge?

The phosphate group Signup and view all the answers

In gel electrophoresis, what property of nucleotides is utilized?

Their negative charge Signup and view all the answers

In Z DNA, which bases may be in syn conformation?

Purines Signup and view all the answers

What characteristic shape does Z DNA have?

Zig-zag form Signup and view all the answers

What are the two main types of nucleic acids?

Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA) Signup and view all the answers

What component distinguishes ribose from deoxyribose?

Presence of a hydroxyl group on the 2' carbon Signup and view all the answers

Which pair of nitrogen bases are classified as purines?

Adenine and Guanine Signup and view all the answers

Which modified base is found in DNA?

5-methyl cytosine Signup and view all the answers

What is a notable function of modified bases in nucleic acids?

They assist in oligonucleotide recognition Signup and view all the answers

What structural feature allows nitrogen bases in nucleotides to stack?

They are planar and have specific conformations Signup and view all the answers

Which of the following components is NOT part of a nucleotide?

Amino acid Signup and view all the answers

How are the carbon atoms in the sugar of a nucleotide numbered?

Using Arabic numerals from 1 to 5 Signup and view all the answers

What type of linkage forms the backbone of nucleic acids?

Phosphodiester linkage Signup and view all the answers

Which base is not found in RNA?

Thymine Signup and view all the answers

Study Notes

Nucleic Acids

Nucleic acids store information for cellular growth and reproduction.
Two main types:
- Deoxyribonucleic acid (DNA)
- Ribonucleic acid (RNA)
Composed of long chains of monomers known as nucleotides.

Nucleotide Structure

A nucleotide consists of:
- Pentose sugar (ribose for RNA, deoxyribose for DNA).
- Nitrogen base.
- Phosphate group.
Sugar C-atoms are numbered as 1’, 2’, 3’, 4’, 5’ for differentiation from nitrogen bases.

Nitrogen Bases

Nitrogen bases are planar, allowing them to stack.
Types of nitrogen bases:
- Purines: Adenine (A) and Guanine (G) - bicyclic structure.
- Pyrimidines: Cytosine (C), Thymine (T), Uracil (U) - monocyclic structure.

Modified Bases

Nucleic acids may include modified bases:
- 5-methyl cytosine (DNA)
- N6-methyl adenine (DNA)
- N6,N6-dimethyl adenine (RNA)
- Pseudouracil (RNA)
- Methylated bases serve functional roles in DNA and RNA.

Functions of Modified Bases

Modified bases assist in oligonucleotide recognition.
Methylation can prevent gene expression and regulate RNA half-life.

Nucleosides and Nucleotides

A nucleoside consists of a nitrogen base linked to a sugar via a glycosidic bond.
Nucleotide production involves attaching a phosphate group to the sugar's C5’ OH group.
Nucleosides are named with suffixes:
- “-osine” for purines.
- “-idine” for pyrimidines.

Conformations and Properties

Nucleosides in DNA typically adopt the anti conformation.
Exception: Guanosine monophosphate can adopt the syn conformation.
Nucleotides absorb UV light at 260nm, useful for quantifying and checking DNA purity.
Nucleotides carry a negative charge due to phosphate groups, important for gel electrophoresis.

Summary

Nucleic acids are critical for life, with complex structures optimizing their function.
Understanding nucleotides and their properties aids in molecular biology and genetics.

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Description

This quiz explores the fundamental concepts of nucleic acids, including their structure, types, and functional roles. You'll learn about the components of nucleotides, the classification of nitrogen bases, and the significance of modified bases in DNA and RNA. Test your knowledge on these crucial biomolecules essential for cellular growth and reproduction.