View Full Version : Y Chromosome Isn't Defective Afterall
Tsukuru
06-19-2003, 01:43 PM
Male Chromosome Map Shows Men Go It Alone (http://abcnews.go.com/wire/SciTech/reuters20030618_413.html)
If you've ever taken any sort of biology course, then you know that the Y chromosome, found only in males, is greatly inferior to the X chromosome. The recent findings showed that the Y chromosome can repair itself without relying on the other chromosome as X chromosomed do in women.
For those who don't know each person has two chromosomes, males having X Y and females X X. The Y chromosome is considered inferior because when the genes from mom and dad are put together it gets all of the 'bad' genes that cause defects.
ShadowTiger
06-19-2003, 01:51 PM
Wow. No wonder I wanted to be a biologist when I grew up. Heh. Good to know, I guess. :laughing:
plith
06-19-2003, 02:01 PM
Actually, I was led to believe that Y is supposed to be inferior to X because in all cases on those two chromosomes that decide any non-sexual trait, the X chromosome is considered dominant. "Bad genes"?
Tsukuru
06-19-2003, 02:55 PM
Well that's what I meant. The Y chromosome receives all of the recessive genes. If the X chromosome also by chance has the recessive genes the negative characteristics will show up in the person.
Jigglysaint
06-19-2003, 06:39 PM
Well if I remember correctly, an X chromosome is a carrier, meaning that more often than not, a person has the bad gene, but doesn't show it. The Y, which isn't passed(I think) is what causes then genes to show. I'm mostly wrong however.
If you don't care about what I learned in Bio, skip this entire post.
The Y (often) doesn't do anything. The X has recessive and dominant traits, and the Y does not. When it comes to determining if someone has an X linked genetic defect, the Y is ignored completely. If the man has an "X" (dominant) then that shows up, and if he has an "x" it is recessive. If a woman has an "XX" or "Xx" or "xX", she receives dominant traits. "xx" is the only possible way for a woman to receive a recessive trait. Colorblindness is one of the main X-linked genetic defects, and men have it far more frequently than women. Also, a defective male can only pass on defective traits, while a "Xx" female can pass one only one of the traits, either "X" or "x."
Punnet Squares help with this concept.
x y
__________
X | Xx | Xy |
|-----+----+
x | xx | xy |
¯¯¯¯¯¯¯¯¯¯
For explanation, box #'s are as follows:
12
34
The man is on top, with x y distributed evenly among the four possible offspring (the boxes) the female is on the left.
The woman's X goes to box 1 and 2, the man's x goes 1 and 3.
The man's y to 2 and 4, and the woman's x to 3 and 4.
The outcomes are a carrier woman, and unaffected boy, an affected girl and an affected boy.
inori
06-20-2003, 05:13 AM
The main "problem" with the Y chromosome is that it is significantly smaller than the X. Put simply, it doesn't have all the genes that its partner, the X chromosome, does.
Think of it this way:
- Gun X (which in this analogy is the normal X chromosome) is fully functional. If you have at least one gun X, you can hit the target.
- Gun x (which is an X chromosome carrying a sex-linked trait, say color-blindness) is defective; the sights aren't aligned. You can't hit the target with an x gun.
- Gun Y (which is a Y chromosome) is missing the trigger, the hammer, and half of the barrel. Oh, and the bullets. Asking whether gun Y can hit the target is irrelevant; gun Y can't even fire.
Girls get two X chromosomes, so they have two chances to hit the target. Guys get an X and a Y, so they only have one chance... if their one X chromosome has a sex-linked gene, they'll "miss the target."
TheGeepster
06-20-2003, 08:40 PM
I did hear something interesting about the Y-chromosome, traditionally thought of as holding junk. Apparently a researcher found that the Y-Chromosome does have ability to repair itself due to a palindromic nature.
Can't verify that though. Something tells me genetics can get very hairy with some of the more complicated aspects, although on it's simplest level, it's merely a matter of relatively simple probabilities.
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