Exploring Chromatin Structure and Topoisomerase

What are the two main types of topoisomerases?

• Type II and Type IV topoisomerases

• Type I and Type II topoisomerases

• Type I and Type III topoisomerases

• Type A and Type B topoisomerases

Describe the structure of a nucleosome.

• A nucleosome consists of two DNA strands intertwined.

• A nucleosome is a single strand of RNA.

• A nucleosome is made up of a lipid bilayer surrounding DNA.

• A nucleosome consists of DNA wrapped around a histone octamer, composed of eight histone proteins.

What is the primary function of histones in DNA packaging?

• To replicate DNA during cell division.

• To provide energy for DNA synthesis.

• The primary function of histones in DNA packaging is to condense and organize DNA into chromatin.

• To protect DNA from environmental damage.

Name one type of histone modification and its effect.

• Ubiquitination of histones, which decreases DNA accessibility.

• Methylation of histones, which inhibits gene transcription.

• Phosphorylation of histones, which has no effect on gene expression.

• Acetylation of histones, which promotes gene transcription.

What role do topoisomerases play during DNA replication?

• Topoisomerases repair DNA damage after replication.

• Topoisomerases act as helicases to unwind DNA.

• Topoisomerases synthesize new DNA strands during replication.

• Topoisomerases relieve torsional strain and prevent supercoiling during DNA replication.

Explain the difference between Type I and Type II topoisomerases.

• Type I topoisomerases are involved in DNA replication, while Type II topoisomerases are not.

• Type I topoisomerases only unwind DNA, while Type II topoisomerases only rewind it.

• Type I topoisomerases cut both strands of DNA, while Type II topoisomerases cut one strand.

• Type I topoisomerases cut one strand of DNA, while Type II topoisomerases cut both strands.

How does the nucleosome core particle contribute to DNA compaction?

• The nucleosome core particle allows DNA to remain completely unwrapped.

• The nucleosome core particle increases the length of DNA strands.

• The nucleosome core particle prevents DNA from folding altogether.

• The nucleosome core particle compacts DNA by wrapping it around histone proteins, reducing its length and facilitating further folding.

What is the impact of histone methylation on chromatin structure?

• Histone methylation has no effect on chromatin structure or gene expression.

• Histone methylation can either compact or relax chromatin structure, influencing gene expression.

• Histone methylation only relaxes chromatin structure, never compacts it.

• Histone methylation exclusively leads to increased gene expression.

Describe the relationship between chromatin structure and transcriptional activity.

• Closed chromatin enhances transcriptional activity.

• Open chromatin inhibits transcriptional processes.

• Chromatin structure directly affects transcriptional activity; open chromatin promotes transcription, while closed chromatin inhibits it.

• Transcriptional activity has no relation to chromatin structure.

What are the components of a nucleosome?

• Histone proteins (H1, H2A, H3) and RNA

• Histone proteins (H2A, H2B, H3, H4) and DNA.

• DNA and lipids

• RNA and ribosomes