Histones and Looped Domains Quiz

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Questions and Answers

What is the primary function associated with looped domains?

Replication of organellar genomes

Co-regulation of gene expression in specific genome areas (correct)

Transcription of all genes in the genome

Packaging DNA into chromosomes

Which process results in tighter packaging of chromosomes?

Prophase of mitosis

Metaphase of mitosis (correct)

G1 phase of interphase

Telophase of mitosis

Which structure helps in the condensing of chromosomes during cell division?

Centromere

Topoisomerase II (correct)

Nuclear envelope

Chromatin fibers

Where are eukaryotic plasmids primarily found?

In fungi, algae, and higher plants Signup and view all the answers

How do chromosome numbers relate to the complexity of an organism?

Chromosome numbers vary independently of organism complexity Signup and view all the answers

What is currently unclear about eukaryotic plasmids?

Their origins Signup and view all the answers

Which genetic elements are often found in the genomes of eukaryotic plasmids?

Organellar genomes Signup and view all the answers

What describes the relationship between organellar genomes and their ancestral organisms?

They resemble the genomes of their ancestors Signup and view all the answers

In which cellular phase is there looser packaging of chromatin to allow transcription?

Interphase Signup and view all the answers

Are there any known eukaryotic Adnaviria currently?

No known eukaryotic Adnaviria exist Signup and view all the answers

What separates sister chromatids in a chromosome?

Centromere Signup and view all the answers

Which statement about the relationship between prokaryotic and eukaryotic plasmids is true?

Some eukaryotic plasmids may be derived from prokaryotic plasmids Signup and view all the answers

Which of the following statements about chromosome organization is correct?

Chromosome organization is poorly understood Signup and view all the answers

Which of the following is a significant challenge in studying eukaryotic plasmids?

Unclear evolutionary origins Signup and view all the answers

What role do plasmids play in organellar genomes?

They contribute to genetic diversity Signup and view all the answers

In the context of eukaryotic viruses, which statement is true?

Six established realms exist for eukaryotic viruses Signup and view all the answers

What is the role of H1/H5 histones in chromatin structure?

They stabilize chromatin and determine nucleosomal repeat length. Signup and view all the answers

Which amino acids are primarily involved in histones' electrostatic interactions with DNA?

Arginine and Lysine Signup and view all the answers

How does lysine acetylation affect histone-DNA interactions?

It decreases binding affinity leading to less stability. Signup and view all the answers

What is the approximate length of DNA wound around a core octamer structure in a nucleosome?

150 bp Signup and view all the answers

What is the term for the complex formed when a linker histone binds to DNA?

Chromatosome Signup and view all the answers

Which of the following statements about histones is incorrect?

Histones are negatively charged. Signup and view all the answers

What is a characteristic effect of post-translational modifications of histones?

They can influence replication, transcription, and repair processes. Signup and view all the answers

What function does the linker histone primarily serve?

To stabilize the overall chromatin structure. Signup and view all the answers

What is indicated about the structure of eukaryotic DNA?

Eukaryotic DNA undergoes complex condensing processes with various histones. Signup and view all the answers

Which of the following statements about organelles is correct?

Both mitochondria and chloroplasts possess their own genomes. Signup and view all the answers

What is the current understanding of chromatin fibre structures?

The dominance of either 10 nm or 30 nm fibres remains unclear. Signup and view all the answers

What does the term 'rampant transfer of genes' refer to?

Gene transfer between organelles and nuclear genomes throughout evolution. Signup and view all the answers

Which statement accurately describes eukaryotic plasmids?

Eukaryotic plasmids are evolutionarily linked to prokaryotic plasmids. Signup and view all the answers

What is the composition of the genome architecture of Marchantia polymorpha?

8 Autosomes + 1 allosome Signup and view all the answers

What type of organism does Marchantia polymorpha represent?

Liverwort Signup and view all the answers

What additional feature can be found in the chloroplast genome of Marchantia polymorpha?

Plasmid for transformation Signup and view all the answers

In what year was the genome assembly of Marchantia polymorpha published?

2020 Signup and view all the answers

Which of the following is NOT included in the molecular evolution insights of Marchantia polymorpha?

Environmental adaptability Signup and view all the answers

Who contributed to the research on gene content and organization in Marchantia polymorpha?

Fukuzawa H. and Kohchi T. Signup and view all the answers

What is the primary focus of the studies mentioned in the context of Marchantia polymorpha?

Genomic architecture and organellar genomes Signup and view all the answers

How many genes are typically found in the mitochondrial genome of Marchantia polymorpha?

About 77 genes Signup and view all the answers

Study Notes

Histones

Histones are proteins that package and order DNA into nucleosomes. They are composed of positively charged amino acids, mainly arginine and lysine, which interact electrostatically with negatively charged DNA.
There are five canonical histones: H1/H5, H2A, H2B, H3, and H4. Of these, H1/H5 acts as a linker histone and determines the nucleosomal repeat length, stabilizing chromatin.
Histones can be post-translationally modified, affecting replication, transcription, and repair processes. Acetylation of positively charged lysine, for example, reduces its affinity for DNA, leading to less stable chromatin.
A nucleosome is formed when roughly 150 base pairs (bp) of DNA are wound around a core octamer structure of histones.
A chromatosome is formed when a linker histone binds roughly 10 bp of DNA at the entry and exit points of a nucleosome.

Looped Domains

Looped domains, also known as topologically associated domains, are poorly understood and still under active investigation.
They appear to be conserved across generations and may be related to the co-regulation of gene expression in specific regions of the genome.
Looped domains may be associated with different expression patterns in various tissue types.

Chromosomes

Chromosomes are formed by the condensing of DNA through the action of Topoisomerase II and the condensin complex.
Most eukaryotes have multiple pairs of linear chromosomes located within the cell nucleus.
These chromosomes are categorized as either autosomes or allosomes.
In interphase, chromatin is less tightly packed, allowing for access to the DNA for transcription.
In metaphase, chromatin is more tightly packed, and each chromatid is a double-stranded DNA double helix.
Sister chromatids are joined at the centromere.

Chromosome Numbers

The number of chromosomes varies significantly across different species.
The complexity of an organism is not necessarily correlated with the number of chromosomes it possesses.

Organellar Genomes

The genomes of mitochondria and chloroplasts resemble those of the organisms from which they originated: alphaproteobacteria and cyanobacteria.
This similarity is a result of primary endosymbiosis, where an early Asgardarchaeon formed a close association (syntrophy) with an early alphaproteobacterium.

Eukaryotic Plasmids

Eukaryotic plasmids are primarily found in fungi, algae, and higher plants.
Their origins are unclear and poorly understood.
Some eukaryotic plasmids are thought to have originated from prokaryotic plasmids.
There is a frequent exchange between genes found in organellar genomes and those found in plasmids.

Eukaryotic Viruses

There are six established realms of viruses, but there are currently no known eukaryotic Adnaviria.

Example of Eukaryotic Genome Architecture: Marchantia polymorpha

The liverwort Marchantia polymorpha has 8 autosomes and 1 allosome.
M. polymorpha has a mitochondrial genome and a chloroplast genome, which can house plasmids for transformation.

Quick Lecture Recap

Eukaryotic DNA undergoes complex condensing processes involving several histones with distinct structures and functions.
The dominant form of chromatin fiber – 10 nm or 30 nm - is still under investigation.
Looped domains of chromatin fibers, though poorly understood, may be associated with co-regulated regions on the genome.
Further condensation leads to the formation of chromosomes.
Mitochondria and chloroplasts possess their own genomes, which have been influenced by extensive gene transfer during evolution.
Eukaryotic plasmids have been linked to the evolution of prokaryotic plasmids.
There are numerous eukaryotic viruses, and some single-stranded DNA viruses may have originated from plasmids.

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Description

Test your knowledge on histones and looped domains with this engaging quiz. Learn about the structure, functions, and modifications of histones as well as the significance of topologically associated domains. Challenge yourself to deepen your understanding of chromatin organization!