DNA Structure and Function Quiz

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Questions and Answers

What type of modifications can histones undergo to alter chromatin structure?

Hydrolysis and condensation

Polymerization and demethylation

Addition and removal of acetyl, phosphate, or methyl groups (correct)

Phosphorylation and oxidation

What is the source of energy for ATP-dependent chromatin-remodeling complexes to reposition DNA?

NADH oxidation

ADP phosphorylation

GTP synthesis

ATP hydrolysis (correct)

Which of the following statements about the chromatin-remodeling complex is accurate?

It is involved in exposing or hiding sequences of DNA. (correct)

It consists of only one subunit that hydrolyzes ATP.

It contains no recognition components for modified histones.

It cannot function without DNA binding proteins.

How many subunits are reported to be part of the chromatin-remodeling complex from yeast?

15 subunits Signup and view all the answers

What is the primary action performed by the chromatin-remodeling complex on DNA?

Loosening nucleosomal DNA and repositioning it Signup and view all the answers

What is the primary function of specialized proteins associated with DNA packaging?

To fold and organize DNA into manageable structures Signup and view all the answers

What is the main characteristic that differentiates eukaryotic chromosomes from bacterial chromosomes?

Eukaryotic chromosomes are linear, while bacterial chromosomes are circular Signup and view all the answers

Which of the following statements about gene expression is true?

Some genes have RNA as their final product Signup and view all the answers

What occurs during cell division in relation to chromosomes?

Duplicated chromosomes are evenly distributed to daughter cells Signup and view all the answers

What are the components of a nucleotide in DNA?

A nitrogenous base, a five-carbon sugar, and a phosphate group Signup and view all the answers

What type of molecules do protein-coding genes produce?

RNA molecules Signup and view all the answers

Which of the following best describes the function of the coils and loops formed during DNA packaging?

They help condense the DNA and prevent tangling Signup and view all the answers

Which bases are found in DNA nucleotides?

Adenine, thymine, guanine, and cytosine Signup and view all the answers

In eukaryotic cells, what happens after DNA has been transcribed into RNA?

The RNA directs the production of a specific protein Signup and view all the answers

What type of bond holds the two strands of DNA together?

Hydrogen bonds Signup and view all the answers

What sugar is found in the nucleotides of DNA?

Deoxyribose Signup and view all the answers

What role do histone tails play in chromatin structure?

They undergo reversible, covalent chemical modifications. Signup and view all the answers

Which is a characteristic of prokaryotic DNA compared to eukaryotic DNA?

It is associated with different types of proteins for packaging Signup and view all the answers

Which of the following is true about the structure of DNA?

DNA has two strands that are complementary and antiparallel Signup and view all the answers

Why are histones considered highly conserved proteins?

Their amino acid sequences show very few differences across species. Signup and view all the answers

What determines the hereditary information stored in DNA?

The sequence of nitrogenous bases Signup and view all the answers

How does the packing of nucleosomes in chromatin differ in living cells from what is typically illustrated?

Nucleosomes stack on top of each other to create a compact structure. Signup and view all the answers

What is the approximate size of the nucleosome core particle?

11 nm Signup and view all the answers

Which statement correctly describes the directionality of DNA strands?

One strand is oriented 5' to 3', and the other is oriented 3' to 5' Signup and view all the answers

What is the significance of the complementary nature of DNA strands?

It allows for the strands to replicate without error Signup and view all the answers

Which of the following statements about DNA-histone interactions is true?

Electrostatic interactions are crucial for DNA binding to histones. Signup and view all the answers

What is a significant characteristic of the amino acid sequence of histone H4?

It is highly conserved with only two differences between species. Signup and view all the answers

Which mechanism allows for the control of chromatin structure?

Histone Tail Modifications. Signup and view all the answers

What is the primary function of histones in eukaryotic cells?

To manage the structure and compactness of chromatin. Signup and view all the answers

What is the diameter of the chromatin fiber formed from packed nucleosomes?

30 nm Signup and view all the answers

Which structure is formed after the chromatin fiber is further folded into loops?

Mitotic chromosome Signup and view all the answers

What is the final packaging ratio of a DNA molecule when it is transformed into a mitotic chromosome?

10,000-fold shorter Signup and view all the answers

What types of proteins assist in driving the condensation of chromatin?

Both histone H1 and specialized non-histone proteins Signup and view all the answers

What is the diameter of the entire mitotic chromosome structure?

1400 nm Signup and view all the answers

Which type of proteins are known to be abundant and assist in chromosome condensation?

Non-histone protein condensins Signup and view all the answers

What enables rapid access to the underlying DNA during chromatin packaging?

Adjustable packaging of DNA Signup and view all the answers

What is currently uncertain regarding the structures involved in chromatin condensation?

The actual structures of chromatin condensation Signup and view all the answers

Study Notes

Structure of DNA

DNA is a double-stranded helix with two polynucleotide chains.
Each strand consists of four types of nucleotides: adenine (A), cytosine (C), guanine (G), and thymine (T).
Nucleotides are composed of a nitrogen-containing base, a five-carbon sugar (deoxyribose), and a phosphate group.
The two strands of DNA are held together by hydrogen bonds between the bases.
A pairs with T, and C pairs with G.

Packaging of DNA

DNA is packaged into chromosomes to fit within the nucleus.
Proteins bind to and fold DNA, generating coils and loops to prevent tangling.
These folded structures allow access for enzymes and proteins involved in replication, repair, and gene expression.

Genes and Proteins

Most genes contain instructions for protein production.
Genes are transcribed into RNA molecules, which then direct protein synthesis.
Some genes produce RNA molecules as their final product.

Eukaryotic Chromosomes

Eukaryotic chromosomes are organized into compact structures.
They are composed of DNA and proteins, primarily histones.
Histones form nucleosomes, which are the basic units of chromatin.

Nucleosomes

A nucleosome consists of a histone octamer (two each of H2A, H2B, H3, and H4) with DNA wrapped around it.
Histones have unstructured N-terminal tails that are subject to reversible modifications, controlling chromatin structure.

Chromosome Organization

Nucleosomes are further packed together to form a 30 nm chromatin fiber.
The chromatin fiber is then folded into loops, creating higher levels of organization.
This packaging allows DNA to be condensed and folded into mitotic chromosomes.

Regulation of Chromosome Structure

Chromatin structure is dynamic and can be adjusted to regulate gene expression.
ATP-dependent chromatin-remodeling complexes can reposition DNA around nucleosomes.
These complexes use ATP hydrolysis to loosen or tighten the DNA, making it accessible or unavailable to other proteins.
Modifications to histone tails, such as acetylation, phosphorylation, and methylation, also influence chromatin structure.

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Description

Test your knowledge on the structure of DNA, how it is packaged into chromosomes, and its role in encoding genes and proteins. This quiz covers key concepts such as nucleotide composition, base pairing, and gene expression mechanisms.