News tagged with chromosomes

Related topics: genes , genome , cells , dna , cell division

Exploring the genetic origins of autism

The geneticist Sébastien Jacquemont is the new holder of the Canada Research Chair in Genetics of Neurodevelopmental Disorders and Associated Dysregulation in Energy Balance at the University of Montreal. He moved to the ...

Feb 25, 2015
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New clues to causes of birth defects

Researchers at Albert Einstein College of Medicine of Yeshiva University have found a possible clue to why older mothers face a higher risk for having babies born with conditions such as Down syndrome that ...

Feb 19, 2015
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Deconstructing the dynamic genome

Two international teams of researchers led by Ludwig San Diego's Bing Ren have published in the current issue of Nature two papers that analyze in unprecedented detail the variability and regulation of gene expression across ...

Feb 18, 2015
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Seven genes for X-linked intellectual disability

X-linked intellectual disability is a disorder that predominantly affects men and can have highly variable clinical manifestations. Scientists at the Max Planck Institute for Molecular Genetics in Berlin ...

Feb 13, 2015
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Team studies blood test for prostate cancer

Vanderbilt University researcher William Mitchell, M.D., Ph.D., and colleagues in Germany and Canada have demonstrated a method for detecting "cell-free" tumor DNA in the bloodstream.

Jan 05, 2015
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New insight into cancer defense mechanism

Researchers at the University of Copenhagen have identified a new mechanism which gives a better understanding of cancer development. The results have just been published in the scientific journal Nature Co ...

Dec 10, 2014
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Stressed-out cancers may provide drug target

Research at the University of Adelaide has discovered cancer cells may be particularly susceptible to metabolic stress – opening the way for new targeted therapy that won't harm normal cells.

Dec 02, 2014
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Chromosome

A chromosome is an organized structure of DNA and protein that is 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. The word chromosome comes from the Greek χρῶμα (chroma, color) and σῶμα (soma, body) due to their property of being very strongly stained by particular dyes. Chromosomes vary widely between different organisms. The DNA molecule may be circular or linear, and can be composed of 10,000 to 1,000,000,000 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. Furthermore, 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 aberrantly evade apoptosis leading to the progression of cancer.

However, in practice "chromosome" is a rather loosely defined term. In prokaryotes, a small circular DNA molecule may be called either a plasmid or a small chromosome. These small circular genomes are also found in mitochondria and chloroplasts, reflecting their bacterial origins. The simplest chromosomes are found in viruses: these DNA or RNA molecules are short linear or circular chromosomes that often lack any structural proteins.

This text uses material from Wikipedia licensed under CC BY-SA