Diseases, Conditions, Syndromes

For this mom, rare bone disease is a family affair

Most people expect some risk in activities like mountain biking or rollerblading, but few would expect to end up in the emergency room with a broken thigh bone from doing a squat.

Genetics

Fat-absorbing XX chromosomes raise heart disease risk in women

New research at the University of Kentucky has confirmed that the presence of XX sex chromosomes increases the amount of fat circulating in the blood, which leads to narrowing of the arteries and ultimately a higher risk ...

Genetics

APOE variants' effect on mortality studied in 38,000

A new study of 38,537 persons of European ancestry suggests that a rare variation of a gene called APOE may be protective and prolong life, in sharp contrast to a more widely studied APOE variant that increases risk of death.

Oncology & Cancer

Overstuffed cancer cells may have an Achilles' heel

In a study using yeast cells and data from cancer cell lines, Johns Hopkins University scientists report they have found a potential weak spot among cancer cells that have extra sets of chromosomes, the structures that carry ...

Medications

Using a common anticonvulsant to counteract inflammation

Serious conditions, including sepsis, stem from inflammation in the body, and there is a lack of effective medication for sepsis. A chromosomal protein called high-mobility group box 1 (HMGB1), secreted by immune and dying ...

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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