BBT 302: Nucleic Acids and Vitamins

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Questions and Answers

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?

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?

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?

Caffeine Signup and view all the answers

What modification occurs to the name of purines when forming nucleosides?

The ending changes to -osine. Signup and view all the answers

What type of sugar is found in RNA nucleotides?

Ribose Signup and view all the answers

Which of the following nitrogen bases is categorized as a purine?

Adenine Signup and view all the answers

Which modified base is commonly found in DNA?

5-methyl cytosine Signup and view all the answers

How are the carbon atoms in the sugar of nucleotides numbered?

1’-5’ Signup and view all the answers

Which nitrogen base is not found in DNA?

Uracil Signup and view all the answers

What is the primary role of nucleic acids?

Information storage for cellular processes Signup and view all the answers

How are nucleotides named?

Using the name of the nucleoside followed by 5'-monophosphate Signup and view all the answers

Which base pairing rule correctly describes the pairing in DNA?

Adenine with Thymine Signup and view all the answers

What type of linkage forms between nucleotides in nucleic acids?

Phosphodiester linkage Signup and view all the answers

In which conformation do nucleosides typically adopt in the DNA duplex?

Anti conformation with some exceptions Signup and view all the answers

What distinguishes deoxyribonucleic acid (DNA) from ribonucleic acid (RNA) at the sugar level?

DNA contains deoxyribose, RNA contains ribose Signup and view all the answers

What is the significance of the absorption of UV light at 260nm by nucleotides?

It is useful for quantifying DNA and checking its purity Signup and view all the answers

Which modified base is typically associated with RNA?

7-methylguanine Signup and view all the answers

What unique property of nucleotides facilitates their movement in gel electrophoresis?

Negative charge due to the phosphate group Signup and view all the answers

Which nucleoside is an exception by adopting the syn conformation?

Guanosine Signup and view all the answers

What characteristic shape does Z DNA primarily exhibit?

Zig-zag form Signup and view all the answers

Which properties allow nucleotides to be distinguished during DNA quantification?

Absorption of UV light and negative charge Signup and view all the answers

What can be inferred about the conformations of purines and pyrimidines in Z DNA?

Purines in syn conformation and pyrimidines in anti Signup and view all the answers

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)
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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Description

This quiz explores the foundations of nucleic acids and their role in cellular functions. Key topics include nucleotides, the formation of phosphodiester linkages, and the Watson-Crick model of DNA. Test your understanding of these essential molecules and their importance in biology.