Robertsonian translocation
A common and significant type of chromosome rearrangement that is formed by fusion of the whole long arms of two acrocentric chromosomes (chromosomes with the centromere near the very end). One in about 900 babies is born with a Robertsonian translocation making it the most common kind of chromosome rearrangement known in people. All five of the acrocentric chromosomes in people — chromosome numbers 13, 14, 15, 21 and 22 — have been found to engage in Robertsonian translocations. However, the formation of Robertsonian translocations was discovered by Hecht and coworkers to be highly nonrandom. Far and away the most frequent forms of Robertsonian translocations are between chromosomes 13 and 14, between 13 and 21, and between 21 and 22.
In balanced form, a Robertsonian translocation takes the place of two acrocentric chromosomes and results in no problems for the person carrying it. But in unbalanced form, Robertsonian translocations produce chromosome imbalance and cause syndrome of multiple malformations and mental retardation. Robertsonian translocations between chromosomes 13 and 14 (when transmitted in unbalanced for may lead to Trisomy 13) lead to the trisomy 13 (Patau) syndrome. And the Robertsonian translocations between 14 and 21 and between 21 and 22 (may result in Trisomy 21) in (trisomy 21 (Down) syndrome.
Robertsonian translocations are named for the America insect geneticist W.R.B. Robertson who first described this form of translocation (in grasshoppers) in 1916 and are also known as whole-arm or centric-fusion translocations or rearrangements.
Read Also:
- Robo
Street name for the cough syrup Robitussin which contains dextromethorphan (DXM).
- Robotripping
Street name for the high produced by abuse of the cough syrup Robitussin which contains dextromethorphan.
- Robust
In statistics, a term applied to a test or procedure that is not seriously disturbed by violations of the assumptions on which it is based. For example, it was an “unexpected and robust difference in the rate of events.” (Dr. Harold J. Burstein, in The New England Journal of Medicine, Oct 9, 2003)
- Rock (drug)
A street name given to cocaine that has been processed from cocaine hydrochloride to a ready-to-use free base for smoking. Rather than requiring the more volatile method of processing cocaine using ether, rock cocaine (also called crack) is processed with ammonia or sodium bicarbonate (baking soda) and water and heated to remove the hydrochloride, thus […]
- Rocky Mountain spotted fever (RMSF)
An acute febrile (feverish) disease initially recognized in the Rocky Mountain states, caused by Rickettsia rickettsii transmitted by hard-shelled (ixodid) ticks. Occurs only in the Western Hemisphere. Anyone frequenting tick-infested areas is at risk for RMSF. The onset of symptoms is abrupt with headache, high fever, chills, muscle pain. and then a rash. The rickettsiae […]