News tagged with chromosomes

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

Mutations in cancer often affect the X chromosome

Every case of cancer originates from changes in a person's genetic material (mutations). These usually occur as "somatic mutations" in individual cells during an individual's lifetime, rather than being inherited from a person's ...

Oct 18, 2013
popularity0 comments 0

In prostate cancer prognosis, telomere length may matter

Like the plastic caps at the end of shoelaces, telomeres protect—in their case—the interior-gene containing parts of chromosomes that carry a cell's instructional material. Cancer cells are known to have short telomeres, ...

Sep 26, 2013
popularity0 comments 0

Research finds X doesn't always mark the spot

Research from the University of Bath has found a greater number of 'escaping genes' on the X chromosome than have been previously detected, with implications for the understanding of mental impairment in humans.

Sep 25, 2013
popularity0 comments 0

Cancer: Lymphoma-linked risk factor identified

Follicular lymphoma is often caused by a translocation between chromosomes 14 and 18, resulting in the overexpression of a cancer-causing gene called BCL-2. A research team co-led by A*STAR scientists recently revealed another ...

Sep 25, 2013
popularity0 comments 0

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

Subscribe to rss feed