A sweetener that is found in plants and used as a substitute for sugar. Xylitol is called a nutritive sweetener because it provides calories, just like sugar. However, it is less likely than sugar to contribute to dental caries.
- XYY syndrome
A chromosomal disorder that affects males only, caused by the presence of an extra Y chromosome. Symptoms may include increased height, speech delays, learning disabilities, mild to moderate mental retardation, and behavioral disturbance. Also known as polysomy Y syndrome.
- X chromosome
The sex chromosome that is found twice in normal females and singly, along with a Y chromosome, in normal males. The complete chromosome complement consists of 46 chromosomes, including the 2 sex chromosomes, and is thus conventionally written as 46,XX for chromosomally normal females and 46,XY for chromosomally normal males.
- X (in genetics)
Although the letter X can be used as a symbol in various ways (such as with X-rays, the X-axis of a graph, etc.), “the X ” in genetics and medicine today usually refers to the X chromosome. The X is the sex chromosome that is found twice in chromosomally normal females and singly along with […]
- Y chromosome
The sex chromosome that is found, together with an X chromosome, in most normal males. The Y chromosome contains the unique male-determining gene and the male fitness genes that are active only in the testis and are responsible for the formation of sperm. Other genes on the Y chromosome have counterparts on the X chromosome, […]
- Y chromosome infertility
Male infertility with oligozoospermia (a subnormal number of sperm) or azoospermia (the absence of sperm) caused by deletion or rearrangement of the long arm of the Y chromosome, as demonstrated by chromosome analysis or by molecular studies which may show microdeletions (of region AZFa, AZFb, or AZFc) of the Y chromosome. Y chromosome infertility is […]