Name: how eukaryotic dna fits inside the nucleus
Uploaded: 2025-08-06T09:37:50.000Z
Duration: 58 s
Channel: JoVE

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Genomic DNA in Eukaryotes

- [Istruttore] Negli eucarioti,
il DNA a doppio filamento

è organizzato all'interno di
nuclei legati a una membrana

per poter contenere lo spazio
limitato della cellula.

Al primo livello di compattazione,

il DNA è avvolto saldamente attorno

a delle specifiche proteine, dette istoni.

Il nucleo di un istone e il
DNA avvolto intorno a esso

sono conosciuti insieme come nucleosomi,

l'unità basilare del DNA.

I nucleosomi sono tenuti
insieme da del DNA legante,

con una struttura che
ricorda una collana di perle.

Nel livello successivo, i nucleosomi

e il DNA legante si avvolgono
a spirale per formare le fibre

di cromatina. Infine, delle
proteine fibrose addizionali

compattano la cromatina ancora
di più, permettendo al DNA

di allungarsi in unità
densamente condensate,

note come cromosomi,

a seconda della fase
della divisione cellulare.

Li, Guohong e Danny Reinberg. "Strutture di ordine superiore della cromatina e regolazione genica". Current Opinion in Genetics & Development 21, n. 2 (aprile 2011): 175-86. [<a href="https://doi.org/10.1016/j.gde.2011.01.022" target="__blank">Sorgente</a>]

dna genomico negli eucarioti

Gli eucarioti hanno grandi genomi rispetto ai procarioti. Per inserire i loro genomi in una cellula, il DNA eucatoico è confezionato straordinariamente saldamente all'interno del nucleo. Per raggiungere questo obiettivo, il DNA è strettamente avvolto intorno alle proteine chiamate istoni, che sono confezionati in nucleosomi che sono uniti dal DNA del linker e dalla bobina in fibre di cromatina. Proteine fibrose aggiuntive compattano ulteriormente la cromatina, che è riconoscibile come cromosomi durante alcune fasi della divisione cellulare.

<h4>Il genoma umano misurato in metri</h4>

La maggior parte delle cellule nel corpo umano contiene circa 6 miliardi di coppie di base di DNA imballato in 23 coppie di cromosomi. È difficile immaginare esattamente quanto DNA rappresentino questi numeri, e quindi è difficile capire quanto il DNA densamente imballato debba essere per inserirsi in una cellula. Possiamo ottenere alcune informazioni esprimendo il genoma in termini di lunghezza. Se dovessimo sistemare il DNA di una singola cellula diploide in linea retta, sarebbe lunga circa due metri!

Si noti che gli esseri umani non hanno genomi insolitamente grandi. Molti pesci, anfibi e piante da fiore hanno genomi molto più grandi degli esseri umani. Ad esempio, il genoma aploide della pianta fiorita giapponese Paris japonica contiene circa 50 volte più DNA del genoma umano aploide. Queste cifre sottolineano il lavoro sorprendente che gli istoni e altre proteine di rimodellamento della cromatina devono fare per confezionare il DNA.

DNA genomico negli eucarioti

Eukaryotes have large genomes compared to prokaryotes. To fit their genomes into a cell, eukaryotic DNA is packaged extraordinarily tightly inside the ...

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how eukaryotic dna fits inside the nucleus

Eukaryotic DNA fits inside the nucleus by packing into a highly compact form. Eukaryotes have large genomes compared with prokaryotes, so their DNA must be tightly organized to fit inside one cell.

The process starts when DNA wraps around proteins called histones. These DNA-histone units form nucleosomes, which are connected by linker DNA. The nucleosomes then coil into chromatin fibers, and additional fibrous proteins compact the chromatin even more.

This packed material is called chromatin, and it becomes recognizable as chromosomes during certain stages of cell division. In human cells, there are about 6 billion base pairs of DNA arranged into 23 pairs of chromosomes. If the DNA from one diploid cell were stretched out in a straight line, it would measure about two meters long.

Humans are not unusual in genome size. Many fish, amphibians, and flowering plants have much larger genomes than humans. The Japanese flowering plant Paris japonica has a haploid genome with about 50 times more DNA than the human haploid genome. These examples show how strongly histones and other chromatin remodeling proteins must work to package DNA.

How Eukaryotic DNA Fits Inside the Nucleus

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Most prokaryotes store their DNA in one circular chromosome inside the nucleoid, a region of cytoplasm. This chromosome is double-stranded and tightly wound, or supercoiled, so it fits efficiently inside the cell. Prokaryotes also carry smaller circular DNA pieces called plasmids. Plasmids often carry genes that give bacteria helpful traits. One important example is antibiotic resistance. Bacteria can gain these plasmids and the traits they carry, which can help them adapt to changing...

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Binary fission is a common way that bacteria and archaea reproduce. In this process, one parent cell divides into two parts. Each new cell can then grow to the size of the original parent cell. This is an asexual form of reproduction, so the cells produced are genetically identical. Binary fission can happen very fast. In the time it takes one bacterial cell to divide, the number of cells in the culture doubles. That time is called the doubling time. Escherichia coli cells often divide every...

genomic dna in eukaryotes

Eukaryotic DNA fits inside the nucleus by packing into a highly compact form. Eukaryotes have large genomes compared with prokaryotes, so their DNA must be tightly organized to fit inside one cell. The process starts when DNA wraps around proteins called histones. These DNA-histone units form nucleosomes, which are connected by linker DNA. The nucleosomes then coil into chromatin fibers, and additional fibrous proteins compact the chromatin even more. This packed material is called chromatin,...

interphase

Interphase in the Cell Growth Cycle

Interphase is the stage of the cell cycle when a eukaryotic cell grows and copies its DNA before mitosis. In a typical human cell, the full cell cycle takes about 24 hours, and interphase makes up about 95 percent of that time. It is followed by mitosis, also called M, when the cell divides. After mitosis and cytokinesis, cells enter the G1 phase, or gap 1. During G1, cells grow continuously and prepare for DNA replication. They are metabolically active and copy essential organelles and...

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Cell cycle stages in mitosis show how a eukaryotic cell copies its DNA and then divides into two daughter cells. The cycle is controlled by regulatory systems and by outside signals that affect cell growth and division. In typical human cells, the full cycle takes about 24 hours and includes two major phases. The first is DNA replication during the S phase of interphase. The second is the mitotic, or M, phase, which includes mitosis and cytokinesis. G1 and G2 are the gap stages between these...

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Cancer develops when mutations affect genes that control cell division. Those changes can remove the normal brakes on growth and lead to uncontrolled cell proliferation. Modern science and medicine have improved how cancer is understood and treated, and some patients can now be cured. There is still no single cure for cancer because cancer is not one disease. It is a large group of many diseases. Even when two people have the same mutation in an oncogene or a tumor suppressor gene, their...

key terms and concepts

Learn how eukaryotic DNA is packed into nucleosomes, chromatin fibers, and chromosomes, and why histones are essential for fitting long DNA inside the nucleus.

How Eukaryotic DNA Fits Inside the Nucleus | JoVE K12

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How Eukaryotic DNA Fits Inside the Nucleus

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