How can chromatin structure be modified in eukaryotes?
Histone modification can open chromatin, thus permitting selective binding of transcription factors that, in turn, recruit RNA polymerase II (Turner, 2005). Varying levels and types of histone modifications have been shown to correlate with levels of chromatin activation.
How are eukaryotic chromosomes organized?
In eukaryotes, however, genetic material is housed in the nucleus and tightly packaged into linear chromosomes. Chromosomes are made up of a DNA-protein complex called chromatin that is organized into subunits called nucleosomes.
What eukaryotic process requires chromatin remodeling?
Chromatin remodeling is an important mechanism of regulating eukaryotic gene expression, which makes tightly condensed DNA accessible to various regulatory factors, such as transcription factors and components of DNA replication.
What are some of the steps in eukaryotic transcriptional control?
Stages of eukaryotic gene expression (any of which can be potentially regulated).
- Chromatin structure. Chromatin may be tightly compacted or loose and open.
- Transcription.
- Processing and export.
- mRNA stability.
- Translation.
- Protein processing.
Why are chromatin structure changes essential for transcription in eukaryotic cells?
In eukaryotic cells, chromatin structure plays a role in gene regulation. of histone proteins and DNA methylation are important in these changes.
How do chromatin remodelers change the structure of the chromatin?
Chromatin remodelers have two types of effects on chromatin dynamics: 1) they package genomic DNA, and incorporate histones into the nucleosome, or 2) release DNA from the histones. After DNA replication, chromatin remodelers pack genomic DNA into nucleosomes.
How does the structure of a eukaryotic chromosome during mitosis?
During cell division, eukaryotic chromosomes condense into highly coiled structures. The tight coiling and high degree of organization in this supercoiled DNA facilitate proper segregation during mitosis and cell division.
How are eukaryotic chromosomes different from prokaryotic chromosomes?
In prokaryotes, the circular chromosome is contained in the cytoplasm in an area called the nucleoid. In contrast, in eukaryotes, all of the cell’s chromosomes are stored inside a structure called the nucleus. Each eukaryotic chromosome is composed of DNA coiled and condensed around nuclear proteins called histones.
How does chromatin remodeling occur?
Chromatin remodeling is the rearrangement of chromatin from a condensed state to a transcriptionally accessible state, allowing transcription factors or other DNA binding proteins to access DNA and control gene expression.
How does transcription work in eukaryotes?
Eukaryotic transcription is carried out in the nucleus of the cell and proceeds in three sequential stages: initiation, elongation, and termination. Eukaryotes require transcription factors to first bind to the promoter region and then help recruit the appropriate polymerase.
What changes take place in chromatin structure?
The chromatin state is dynamic, allowing for changes in gene expression in response to cellular signals and/or environmental cues. Changes in chromatin result from the action of ATP-dependent chromatin-remodeling complexes, reversible epigenetic histone modifications, and the incorporation of histone variants.
How does chromatin Remodelling regulate gene transcription?
Chromatin remodeling plays a central role in the regulation of gene expression by providing the transcription machinery with dynamic access to an otherwise tightly packaged genome.
What role do chromatin remodelers play in eukaryotic gene expression?
What role do chromatin remodelers play in eukaryotic gene expression? Chromatin remodeler enzymes can enzymatically change the distribution or composition of nucleosomes (histone octamers). a eukaryotic cis-acting DNA regulatory sequence to which transacting factors bind and stimulate transcription.
How does eukaryotic chromatin become compacted?
The answer to this question lies in the fact that certain proteins compact chromosomal DNA into the microscopic space of the eukaryotic nucleus. These proteins are called histones, and the resulting DNA-protein complex is called chromatin. It may seem paradoxical that proteins are added to DNA to make it more compact.
What are the defining features of eukaryotic chromosomes?
Eukaryotes have [1] a membrane-bound nucleus, [2] intracellular organelles, and [3] a cytoskeleton • Most eukaryotes undergo sexual reproduction •The genome size of eukaryotes spans a wider range than that of most prokaryotes • Eukaryotic genomes have a lower density of genes • Prokaryotes are haploid; eukaryotes have …
Why are eukaryotic chromosomes linear?
A linear chromosome is a chromosome which is linear in shape, and contains terminal ends. In most eukaryotic cells, DNA is arranged in multiple linear chromosomes. In contrast, most prokaryotic cells generally contain a singular circular chromosome.
How does transcription and translation occur in eukaryotes?
Transcription occurs in the nucleus in eukaryotic organisms, while translation occurs in the cytoplasm and endoplasmic reticulum. Both processes occur in the cytoplasm in prokaryotes. The factor controlling these processes is RNA polymerase in transcription and ribosomes in translation.
How is chromatin structure regulated?
Chromatin accessibility is regulated by nucleosome remodeling, utilization of histone variants, DNA methylation, and posttranslational modifications (PTMs). Chromatin remodeling complexes can slide nucleosomes, rotate the DNA helix relative to the nucleosome to expose TF binding sites, or evict nucleosomes.
How chromatin is packaged in a eukaryotic chromosome?
Nucleosomes fold up to form a 30-nanometer chromatin fiber, which forms loops averaging 300 nanometers in length. The 300 nm fibers are compressed and folded to produce a 250 nm-wide fiber, which is tightly coiled into the chromatid of a chromosome.
How does Supercoiling occur in eukaryotic DNA?
In eukaryotes (and archaea encoding histone proteins), which lack DNA gyrase, supercoils are introduced by wrapping of DNA around the nucleosome surface (right panel). These supercoils are constrained on the surface of histone proteins.
In what way are eukaryotic chromosomes different from prokaryotic chromosomes?
What do we know about chromosome rearrangement patterns?
Comparative sequence analyses reveal patterns of apparently random rearrangement interspersed with regions of extraordinarily rapid, localized genome evolution. Numerous subtle rearrangements near centromeres, telomeres, duplications, and interspersed repeats suggest hotspots for eukaryotic chromosome evolution.
What are sister chromatids in eukaryotic cells?
The two kinds of nuclear division processes in eukaryotic cells are called mitosis and meiosis. When a chromosome is replicated before mitosis or meiosis, the two identical copies stay bound to each other at first and are called sister chromatids. A chromatid, then, is one copy of a duplicated chromosome.
What is a chromatid?
The term “chromatid” arose as a term to distinguish each copy of the parent chromosome during the period of time before the copies become independent chromosomes themselves.
What happens when the chromatids separate into new gamete cells?
When the chromatids separate into the new gamete cells, none of them are the same as any of the parental chromatids, because of the genetic exchange that has happened. This increases diversity and contributes to evolution.