Difference between revisions of "Chromosome"

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==Origin==
 
==Origin==
 
German ''chromosom''
 
German ''chromosom''
*[http://en.wikipedia.org/wiki/19th_century 19th Century]
+
*[https://en.wikipedia.org/wiki/19th_century 19th Century]
 
The [[word]] chromosome comes from the [[Greek]] χρῶμα (chroma, [[colour]]) and σῶμα (soma, [[body]]) due to their property of being very strongly stained by particular dyes.
 
The [[word]] chromosome comes from the [[Greek]] χρῶμα (chroma, [[colour]]) and σῶμα (soma, [[body]]) due to their property of being very strongly stained by particular dyes.
 
==Definition==
 
==Definition==
*1: any of the rod-shaped or threadlike [[DNA]]-containing [[structures]] of cellular [[organisms]] that are located in the [[nucleus]] of [http://en.wikipedia.org/wiki/Eukaryote eukaryotes], are usually ring-shaped in [http://en.wikipedia.org/wiki/Prokaryotic prokaryotes] (as bacteria), and contain all or most of the genes of the [[organism]]; also : the genetic material of a [[virus]]
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*1: any of the rod-shaped or threadlike [[DNA]]-containing [[structures]] of cellular [[organisms]] that are located in the [[nucleus]] of [https://en.wikipedia.org/wiki/Eukaryote eukaryotes], are usually ring-shaped in [https://en.wikipedia.org/wiki/Prokaryotic prokaryotes] (as bacteria), and contain all or most of the genes of the [[organism]]; also : the genetic material of a [[virus]]
 
==Description==
 
==Description==
A '''chromosome''' is an organized [[structure]] of [[DNA]] and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other [http://en.wikipedia.org/wiki/Genetic_sequence nucleotide sequences]. Chromosomes also contain DNA-bound [http://en.wikipedia.org/wiki/Protein proteins], which serve to package the DNA and [[control]] its [[functions]].
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A '''chromosome''' is an organized [[structure]] of [[DNA]] and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other [https://en.wikipedia.org/wiki/Genetic_sequence nucleotide sequences]. Chromosomes also contain DNA-bound [https://en.wikipedia.org/wiki/Protein proteins], which serve to package the DNA and [[control]] its [[functions]].
  
Chromosomes vary widely between different [[organisms]]. The [[DNA]] [[molecule]] may be [[circular]] or [[linear]], and can be composed of 100,000 to 10,000,000,000 nucleotides in a long [[chain]]. Typically, [http://en.wikipedia.org/wiki/Eukaryote eukaryotic] cells (cells with [[nuclei]]) have large linear chromosomes and [http://en.wikipedia.org/wiki/Prokaryotic prokaryotic] cells (cells without defined nuclei) have smaller circular chromosomes, although there are many exceptions to this rule. Also, cells may contain more than one type of chromosome; for example, [http://en.wikipedia.org/wiki/Mitochondria mitochondria] in most eukaryotes and chloroplasts in [[plants]] have their own small chromosomes.
+
Chromosomes vary widely between different [[organisms]]. The [[DNA]] [[molecule]] may be [[circular]] or [[linear]], and can be composed of 100,000 to 10,000,000,000 nucleotides in a long [[chain]]. Typically, [https://en.wikipedia.org/wiki/Eukaryote eukaryotic] cells (cells with [[nuclei]]) have large linear chromosomes and [https://en.wikipedia.org/wiki/Prokaryotic prokaryotic] cells (cells without defined nuclei) have smaller circular chromosomes, although there are many exceptions to this rule. Also, cells may contain more than one type of chromosome; for example, [https://en.wikipedia.org/wiki/Mitochondria mitochondria] in most eukaryotes and chloroplasts in [[plants]] have their own small chromosomes.
  
In eukaryotes, nuclear chromosomes are packaged by proteins into a [[condensed]] [[structure]] called [http://en.wikipedia.org/wiki/Chromatin chromatin]. This allows the very long [[DNA]] [[molecules]] to fit into the cell [[nucleus]]. The structure of chromosomes and chromatin varies through the [http://en.wikipedia.org/wiki/Cell_cycle cell cycle]. Chromosomes are the [[essential]] [[unit]] for cellular division and must be replicated, divided, and passed successfully to their daughter cells so as to ensure the genetic [[diversity]] and [[survival]] of their progeny. Chromosomes may exist as either duplicated or unduplicated. Unduplicated chromosomes are single linear strands, whereas duplicated chromosomes (copied during [http://en.wikipedia.org/wiki/S_phase synthesis phase]) contain two copies joined by a [http://en.wikipedia.org/wiki/Centromere centromere].
+
In eukaryotes, nuclear chromosomes are packaged by proteins into a [[condensed]] [[structure]] called [https://en.wikipedia.org/wiki/Chromatin chromatin]. This allows the very long [[DNA]] [[molecules]] to fit into the cell [[nucleus]]. The structure of chromosomes and chromatin varies through the [https://en.wikipedia.org/wiki/Cell_cycle cell cycle]. Chromosomes are the [[essential]] [[unit]] for cellular division and must be replicated, divided, and passed successfully to their daughter cells so as to ensure the genetic [[diversity]] and [[survival]] of their progeny. Chromosomes may exist as either duplicated or unduplicated. Unduplicated chromosomes are single linear strands, whereas duplicated chromosomes (copied during [https://en.wikipedia.org/wiki/S_phase synthesis phase]) contain two copies joined by a [https://en.wikipedia.org/wiki/Centromere centromere].
  
Compaction of the duplicated chromosomes during [http://en.wikipedia.org/wiki/Mitosis mitosis] and meiosis results in the classic four-arm structure (pictured to the right). Chromosomal recombination plays a vital role in [[genetic]] [[diversity]]. If these structures are manipulated incorrectly, through processes known as chromosomal instability and translocation, the cell may undergo [http://en.wikipedia.org/wiki/Mitotic_catastrophe mitotic catastrophe] and die, or it may unexpectedly evade [http://en.wikipedia.org/wiki/Apoptosis apoptosis] leading to the progression of cancer.
+
Compaction of the duplicated chromosomes during [https://en.wikipedia.org/wiki/Mitosis mitosis] and meiosis results in the classic four-arm structure (pictured to the right). Chromosomal recombination plays a vital role in [[genetic]] [[diversity]]. If these structures are manipulated incorrectly, through processes known as chromosomal instability and translocation, the cell may undergo [https://en.wikipedia.org/wiki/Mitotic_catastrophe mitotic catastrophe] and die, or it may unexpectedly evade [https://en.wikipedia.org/wiki/Apoptosis apoptosis] leading to the progression of cancer.
  
In [[practice]] "chromosome" is a rather loosely defined term. In prokaryotes and [[viruses]], the term [http://en.wikipedia.org/wiki/Genophore genophore] is more appropriate when no chromatin is present. However, a large body of work uses the term chromosome regardless of chromatin content. In prokaryotes, [[DNA]] is usually arranged as a circle, which is tightly coiled in on itself, sometimes accompanied by one or more smaller, circular DNA molecules called [http://en.wikipedia.org/wiki/Plasmid plasmids]. These small circular genomes are also found in mitochondria and chloroplasts, reflecting their bacterial origins. The simplest genophores are found in [[viruses]]: these DNA or [http://en.wikipedia.org/wiki/RNA RNA] molecules are short linear or circular genophores that often lack structural proteins.[http://en.wikipedia.org/wiki/Chromosome]
+
In [[practice]] "chromosome" is a rather loosely defined term. In prokaryotes and [[viruses]], the term [https://en.wikipedia.org/wiki/Genophore genophore] is more appropriate when no chromatin is present. However, a large body of work uses the term chromosome regardless of chromatin content. In prokaryotes, [[DNA]] is usually arranged as a circle, which is tightly coiled in on itself, sometimes accompanied by one or more smaller, circular DNA molecules called [https://en.wikipedia.org/wiki/Plasmid plasmids]. These small circular genomes are also found in mitochondria and chloroplasts, reflecting their bacterial origins. The simplest genophores are found in [[viruses]]: these DNA or [https://en.wikipedia.org/wiki/RNA RNA] molecules are short linear or circular genophores that often lack structural proteins.[https://en.wikipedia.org/wiki/Chromosome]
  
 
[[Category: Biology]]
 
[[Category: Biology]]

Latest revision as of 23:45, 12 December 2020

Lighterstill.jpg

Chromosome.jpg

Origin

German chromosom

The word chromosome comes from the Greek χρῶμα (chroma, colour) and σῶμα (soma, body) due to their property of being very strongly stained by particular dyes.

Definition

Description

A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.

Chromosomes vary widely between different organisms. The DNA molecule may be circular or linear, and can be composed of 100,000 to 10,000,000,000 nucleotides in a long chain. Typically, eukaryotic cells (cells with nuclei) have large linear chromosomes and prokaryotic cells (cells without defined nuclei) have smaller circular chromosomes, although there are many exceptions to this rule. Also, cells may contain more than one type of chromosome; for example, mitochondria in most eukaryotes and chloroplasts in plants have their own small chromosomes.

In eukaryotes, nuclear chromosomes are packaged by proteins into a condensed structure called chromatin. This allows the very long DNA molecules to fit into the cell nucleus. The structure of chromosomes and chromatin varies through the cell cycle. Chromosomes are the essential unit for cellular division and must be replicated, divided, and passed successfully to their daughter cells so as to ensure the genetic diversity and survival of their progeny. Chromosomes may exist as either duplicated or unduplicated. Unduplicated chromosomes are single linear strands, whereas duplicated chromosomes (copied during synthesis phase) contain two copies joined by a centromere.

Compaction of the duplicated chromosomes during mitosis and meiosis results in the classic four-arm structure (pictured to the right). Chromosomal recombination plays a vital role in genetic diversity. If these structures are manipulated incorrectly, through processes known as chromosomal instability and translocation, the cell may undergo mitotic catastrophe and die, or it may unexpectedly evade apoptosis leading to the progression of cancer.

In practice "chromosome" is a rather loosely defined term. In prokaryotes and viruses, the term genophore is more appropriate when no chromatin is present. However, a large body of work uses the term chromosome regardless of chromatin content. In prokaryotes, DNA is usually arranged as a circle, which is tightly coiled in on itself, sometimes accompanied by one or more smaller, circular DNA molecules called plasmids. These small circular genomes are also found in mitochondria and chloroplasts, reflecting their bacterial origins. The simplest genophores are found in viruses: these DNA or RNA molecules are short linear or circular genophores that often lack structural proteins.[1]