DNA Structure and Components

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Questions and Answers

What is the primary component of DNA?

Adenine

Histones

Deoxyribonucleotides (correct)

Ribose

In which types of cells is DNA found?

Only in animal cells

In every nucleated cell (correct)

Only in bacteria

Only in plant cells

Which nitrogenous bases are classified as Purines?

Adenine and Thymin

Cytosine and Uracil

Adenine and Guanine (correct)

Thymine and Cytosine

What is the sugar component of DNA?

Deoxyribose Signup and view all the answers

What term was coined by Atlman for the protein-free preparation of nuclei?

Nucleic acid Signup and view all the answers

What makes the nitrogenous bases in DNA negatively charged?

Presence of phosphate groups Signup and view all the answers

How does a nucleoside form?

By the association of a sugar and a nitrogenous base Signup and view all the answers

Which other nitrogenous base complements Adenine in DNA?

Thymine Signup and view all the answers

What type of bond links ribonucleotides together in RNA?

Phosphodiester bond Signup and view all the answers

Where does the phosphate group attach in a deoxyribonucleotide?

C-3' Signup and view all the answers

Which nucleotides serve as the building blocks for DNA?

Deoxyribonucleotides Signup and view all the answers

In a nucleic acid strand, which end is defined by a free hydroxyl group?

3-end Signup and view all the answers

What type of structural unit is a deoxyribonucleotide composed of?

Base, sugar, and phosphate Signup and view all the answers

Which atom in the nitrogenous base of a nucleotide is typically linked to the sugar?

N-1 Signup and view all the answers

What kind of bond forms between the monosaccharide units of polysaccharides?

Glycosidic bond Signup and view all the answers

Which functional group does the phosphate group attach to in a nucleic acid?

Hydroxyl group Signup and view all the answers

What is the primary structural difference between a dinucleotide and a polynucleotide?

A dinucleotide is formed from two nucleotide units, while a polynucleotide consists of many nucleotide units. Signup and view all the answers

What role do hydrogen bonds play in the structure of DNA?

They hold the complementary nitrogenous bases together. Signup and view all the answers

Which carbon of the sugar molecule in a nucleotide is bonded to the nitrogenous base?

The 1st carbon Signup and view all the answers

What feature distinguishes the arrangement of DNA strands in the double helix?

The strands are oriented in an antiparallel arrangement. Signup and view all the answers

Which of the following best defines a nucleotide?

A structure made of a nitrogenous base, sugar, and a phosphate group. Signup and view all the answers

What is considered the functionally important aspect of the order of bases in a polynucleotide?

It determines the genetic information of the molecule. Signup and view all the answers

What two scientists are credited with determining the three-dimensional structure of DNA?

Watson & Crick Signup and view all the answers

In a nucleotide, what connects the 3rd carbon of one sugar to the 5th carbon of the next?

A phosphate group Signup and view all the answers

What is the relationship between Adenine and Thymine in DNA?

They pair with complementary bases. Signup and view all the answers

Which groove of the DNA double helix is wider and more accessible for protein binding?

The major groove. Signup and view all the answers

Which pair of bases is correctly matched according to Chargaff's Rule?

Guanine and Cytosine Signup and view all the answers

How many hydrogen bonds are formed between Adenine and Thymine?

Two Signup and view all the answers

What structure do the glycosidic bonds between sugar and bases form in DNA?

They create unequal grooves. Signup and view all the answers

Which of the following statements about the backbone of DNA is true?

It is composed of deoxyribose and phosphodiester linkages. Signup and view all the answers

Why is the interaction of DNA-binding proteins more favorable with the major groove?

The major groove is less obstructed by the sugar-phosphate backbone. Signup and view all the answers

Which of the following is NOT true about the base pairing in DNA?

Base pairs can form in any arbitrary combination. Signup and view all the answers

What is the most common conformation of DNA?

B-DNA Signup and view all the answers

How many base pairs does one complete turn of the B-DNA double helix consist of?

10.4 base pairs Signup and view all the answers

What is the diameter of the B-DNA double helix?

2.37 nm Signup and view all the answers

In what condition is Z-DNA primarily seen?

High salt concentrations Signup and view all the answers

What type of molecules are prokaryotic DNA typically associated with?

Naked DNA Signup and view all the answers

What is the pitch of the A-DNA helix?

2.46 nm Signup and view all the answers

Which feature differentiates Z-DNA from B-DNA?

Z-DNA is a left-handed helix Signup and view all the answers

What is a feature of eukaryotic DNA compared to prokaryotic DNA?

It resides within a membrane-bound nucleus Signup and view all the answers

Study Notes

DNA Structure

DNA is a polymer of deoxyribonucleotides found in chromosomes, mitochondria, and chloroplasts.
Nuclear DNA is bound to basic proteins called histones.
DNA is present in every nucleated cell and carries genetic information.
DNA is composed of two strands wound around each other to form a double helix with bases inside and sugar-phosphate backbones on the outside.
Two DNA strands are organized in an antiparallel arrangement.
The bases form hydrogen bonds to each other.
Adenine pairs with Thymine, and Guanine pairs with Cytosine. This is called complementary base pairing.

DNA Components

Deoxyribose: A five-carbon sugar that forms the backbone of DNA.
Phosphate Group: A negatively charged group that links deoxyribose molecules together.
Nitrogenous Bases: Adenine, Guanine, Cytosine, and Thymine. Adenine and Guanine are purines; Thymine and Cytosine are pyrimidines.

DNA Nucleotides

Nucleoside: A base bound to a sugar.
Nucleotide: A nucleoside bound to a phosphate group.
Deoxyribonucleotides: Nucleotides containing deoxyribose are the building blocks of DNA.
Ribonucleotides: Nucleotides containing ribose are the building blocks of RNA.

DNA Structure Features

Double helix: DNA has two strands that wind around each other.
Antiparallel: The two strands of DNA have opposite orientations.
Major groove: A wider groove between the two strands of DNA.
Minor groove: A narrower groove between the two strands of DNA.
B-DNA: The most common conformation of DNA. It is a right-handed helix with one turn every 10.4 base pairs.
A-DNA: A right-handed helix that is wider and flatter than B-DNA. It is found in dehydrated conditions or low salt concentrations.
Z-DNA: A left-handed helix with one turn every 12 base pairs. It is found in high salt concentrations.

DNA Polymorphism

DNA can exist in different conformations depending on conditions.

Prokaryotic DNA

Found in bacteria and archaea.
Present as a single circular molecule called a bacterial chromosome.
DNA is naked (without associated histone proteins).

Eukaryotic DNA

Found in more complex multicellular organisms like plants, animals, fungi, and single-celled organisms like amoeba and yeast.
Enclosed within a membrane-bound nucleus.
DNA is bound with histone proteins.

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Description

This quiz covers the fundamental structure of DNA, including its components such as deoxyribose, nitrogenous bases, and nucleotides. Understand how DNA forms a double helix and the significance of complementary base pairing. Test your knowledge of how these elements function together to carry genetic information.