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Y (in chemistry)
The symbol for the element yttrium, an ultrarare metal named after Ytterby in southern Sweden. Yttrium has been used in certain nuclear medicine scans.
Y (in genetics)
The Y chromosome, the sex chromosome found in normal males, together with an X chromosome.
Y chromatin
Brilliantly fluorescent body seen in cells stained with the dye quinacrine which lights up the Y chromosomes most brightly.
Y chromosome
The sex chromosome found in normal males, together with an X chromosome. Once thought to be a genetic wasteland, the Y now is known to contain at least 20 genes, some of them unique to the Y including the male-determining gene and male fitness genes that are active only in the testis and are thought responsible for the formation of sperm. Other genes on the Y have counterparts on the X chromosome, are active in many body tissues and play crucial "housekeeping" roles with the cell.
Y map
The array of genes on the Y chromosome. Once thought to be a genetic wasteland, the Y now is known to contain at least 20 genes, some of them unique to the Y including the male-determining gene and male fitness genes that are active only in the testis and are thought responsible for the formation of sperm. Other genes on the Y have counterparts on the X chromosome, are active in many body tissues and play crucial "housekeeping" roles with the cell.
Y. pestis
Yersinia pestis, the bacteria that causes the bubonic plague which in the year 541 (as the Black Death) and later in the Middle Ages decimated Europe. The effects of the plague are described in the nursery rhyme "We all fall down."
Y. pestis mainly infects rats and other rodents which are the prime reservoir for the bacteria. Fleas are the prime vectors carrying the bacteria from one species to another. They bite rodents infected with Y. pestis, then they bite people and so transmit the disease to them.
Transmission of the plague to people can also occur from eating infected animals such as squirrels. Once someone has the plague, they can transmit it to another person via aerosol droplets.
Plague occurs in the U.S. It is treatable with antibiotics but, if not treated promptly, can promptly lead to death.
Yersinia is named after the Swiss bacteriologist Alexandre- Emile-Jean Yersin (1863-1943) who identifed it in 1894 after a trip to Hong Kong looking for the agent that was killing thousands of people in southern China. The bacteria was also discovered at the same time by the Japanese bacteriologist Shibasaburo Kitasako.
YAC
YAC stands for yeast artificial chromosome, a vector (carrier) created and used in the laboratory to clone pieces of DNA.
A YAC is constructed from the telomeric, centromeric, and replication origin sequences needed for replication in yeast cells. (The telomere is the end of the chromosome; the centromere is the chromosome region to which spindle fibers attach during cell division; and the replication origin sequences are the spots where the replication of DNA starts.)
Yag laser surgery
The use of a laser to punch a hole in the iris to relieve increased pressure within the eye as, for example, from acute angle-closure glaucoma. Yag laser surgery is an office procedure.
Yard
In length, 3 feet or 36 inches or, metrically, 86.44 centimeters. The yard, along with the foot and inch, are English creations to which the USA has stubbornly clung. The yard was originally a unit of measurement of land and was about 5 meters (now termed a rod). In the 14th century, the yard emerged as 3 feet, about the length of a riding stick or sword.
Yawn
Involuntary opening of the mouth, often caused by suggestion. Yawning is characterized by breathing first inward, then outward.
Repeated yawning is often a sign of drowsiness. It can also sometimes be a sign of depression.
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