2006-09-14 02:29:59 · 4 answers · asked by Shan 1 in Science & Mathematics ➔ Biology
x chromosomes are purely (or at least thought to be mostly) used to determine sex, there is a specific gene in the x chromosome (or perhaps a different chromosome) that signals the production of a protein to "stop" x chromosome thus making it a "bar body" (of course in females only, or individuals with extra chromosomes). also since the x chromosome is used mostly for gender and there is not much other critical information in the x chromosome (other then being used in the early stages of human development), it can be shut off and the human can still survive (timing is extremely critical, too late or too early and the person will die). however if a different chromosome was shut off, it would either result in a miscarage (this would happen so readily the female would many times not even know she was pregnant) or would result in some sort of mental or physical illness. these illnesses also occur when an extra chromosome is copied, such as "trisomy 21" (having 3 number 21 chormomes) which results in a person having down syndrome
2006-09-14 02:40:37 · answer #1 · answered by Paul S 2 · 0⤊ 0⤋
Most chromosomes contain genes that produce just enough of their products (proteins, usually) when there are two copies. The genes on the X include some that overdose the person with that protein if two copies of the gene are active. So, the second X is shut off. That makes the female a pseudomale, since the male has only one X so he has only one active X. After the Barr body forms, each female cell has only one active X, but which one is active seems to be chosen randomly. This idea was suggested and tested extensively by Mary Lyon and is called the Lyon hypothesis.
2006-09-17 12:14:58 · answer #2 · answered by Lorelei 2 · 0⤊ 0⤋
Barr bodies are the result of what's known as "random inactivation". This is a process whereby one of a female's two X chromosomes becomes inactivated in every cell in the body, because only one of each pair is necessary for normal function. That inactivated X is what you see as a Barr body. Other chromosomes (the 44 pairs known as autosomes) require BOTH in each pair to be active for proper function, so no need for random inactivation.
2006-09-14 02:36:20 · answer #3 · answered by medrecgal1973 5 · 0⤊ 0⤋
Huh? Clever clogs!
2006-09-14 02:37:05 · answer #4 · answered by Mizzy 3 · 0⤊ 0⤋