Looking up genetics for another question, I found a diagram of the human genes. Why is the "Y" chromosome so much smaller than the "X" chromosome?

TheAlphaWolf

a complete guess but since males already have an X chromosome, there isn't much more to add so you're a functioning male so it's smaller. Mar 13 05, 4:17 PM

kaylofgorons

Females have two Xs and males have X and Y. I know certain information can be stored on an X that cannot fit on a Y. That is why any male with a color blindness gene WILL be colorblind. It is recessive, but he does not have the other X chromosome to suppress it. A female can carry colorblindness and see color just fine if she has the dominant gene. Both her Xs have to have colorblindness for her to be colorblind. I think hemophilia is the same way, as well. So why do guys have less genetic info? Mar 13 05, 4:25 PM

TheAlphaWolf

the bottom line is that we don't need it. :D maybe having another Y can be good for some diseases, but they still code for the same genes and while males have less AMOUNT of genetic info, we have more genes in use (I think...) :) Mar 13 05, 4:29 PM

kaylofgorons

Of course you don't need it. You're alive and typing, aren't you? Don't you mean another X? I've always wondered about this... Mar 13 05, 4:35 PM

Flynn_17

People can be XXY, XYY, and XXYY... XXY are haermaphrodites, I believe, and they tend to be mentally unstable also... there's also XO, but I don't know anything about that. Gimme a mo, I'll find a site. Mar 13 05, 4:38 PM

TheAlphaWolf

oh that's right another X. If you have another Y, you have a really bad disease that I don't remember the name of :P Mar 13 05, 4:41 PM

Flynn_17

http://www.2beornot2be.com/Chromosomes/gc.htm Apparently, you can be YO, too. Mar 13 05, 4:41 PM

Flynn_17

Mass murderers tend to be XYY. http://www.palmersplace.btinternet.co.uk/pages/geneticdisease/geneticdisease.htm Mar 13 05, 4:43 PM

TheAlphaWolf

YO! that's cool! anyway... just notice that they're not true hemaphrodites. true hemaphrodites (like earthworms, snails, etc) are able to reproduce both as males and females. Human "hemaphrodites" just have messed up genitalia. Mar 13 05, 4:43 PM

Flynn_17

I knew a haemaphodite once. He had male genitalia, but every 28 days, he would bleed out of his rectum. He got done for robbing a bank. Mar 13 05, 5:16 PM

Baloo55th

Sure that wasn't piles? Never heard of that in hermaphroditism before. The length of a chromosome doesn't relate to the amount of usable information on it. Much of the genetic code stuff is regarded as 'junk'. They're starting to get a bit worried about this now, though, and thinking that some of it isn't quite as redundant as they first thought. Incidentally, and going a bit off thread, they've decided that the Flores remains are definitely not Homo sapiens, but closer in type to Homo erectus. (New Scientist, last Thursday) Mar 13 05, 6:45 PM

TheAlphaWolf

If the same chromosome (X) codes for the same genes, having one or two doesn't matter because they're still coding for the same genes... right? it's only the amount of the protein produced that would change if you have more than one chromosome. ok fine, the genes would be different but you know what I mean... don't you? if you have two of the same chromosome (let's say you have 5 genes in the X chromosome), maybe 2 on one are recessive so they're not used and 3 are dominant and they are used, and viceversa on the other one... so only 5 genes in total are used(3 dominant from one, 2 dominant from the other. if you have an X and a Y though, all of the 5 genes in X are expressed and even though Y only has 2 genes in it (did I mention I'm just simplifying the numbers? X doesn't have 5 genes and Y doesn't have 2), in total there are two more genes used because you have a different chromosome. Mar 13 05, 6:58 PM

lothruin

It is my understanding that although the X and Y have varying genes, they are still a functioning chromosome pair. In other words, the Y chromosome may contain the information to create testes and other male organs, etc., but those are simply dominant forms of the otherwise "default" matching genes on the X chromosome. I believe Alpha is incorrect in suggesting that in males 7 genes would be used as opposed to 5. All the genes that appear on the Y chromosome have corresponding genes on the X chromosome, they just may be more likely to be dominant on the Y chromosome because of what they are there for. But he is right that you don't need the Y chromosome to be larger. It has roughly 1/3 the number of base pairs as the X chromosome. But the particular data contained on those chromosomes appearantly need not be duplicated on both in order for them to function. There is a concern amongst some that the Y chromosome is slowly dwindeling and may disappear altogether, because it has no pair with which to swap genetic information if a mutation should occur, so when one DOES occur, the junk is eventually abandoned. This is one suggested reason why it is now so much smaller than the X chromosome. But other scientists have done studies that seem to show the Y chromosome has made for itself a way to keep pairs of certain vital genetic code, so that if a mutation occurs in one sequence, the gene can use the other sequence instead. If this is the case, then the Y chromosome may continue to dwindle in size until only the information which makes it's existence neccessary to begin with is still contained on the chromosome. Mar 13 05, 7:39 PM

gmackematix

It's ridiculous, but I have only just noticed that these letters are used because a capital Y is like a capital X with a missing "arm". Mar 13 05, 7:43 PM

TheAlphaWolf

ah! I forgot that they're pairs. I was thinking of them as a different pair of chromosomes. Mar 13 05, 7:50 PM

kaylofgorons

They are the "23rd" pair. Each member of a pair usually has different genes for the same trait. You can have dominent, recessive, and--and, well the traits mix sometimes, like when you have a flowers with white genes and a red genes, but if they're together you get pink, not a dominant or recessive color. So I would imagine the traits that exist on Y are certain important male traits and dominant because it's Y that makes you a guy. There are traits on that X that have no matching traits to oppose them. Therefore colorblindness and hemophelia can become default settings even though they are recessive: Y has nothing to suppress them. I highly doubt that much of our genetic code is "junk". Certain very important parts of my anatomy were once considered "junk". Doctors now refuse to remove tonsils when a few decades ago nearly everyone had their tonsils out. We're just starting to understand DNA--give them a few more years... Mar 13 05, 8:20 PM

kaylofgorons

Do NOT take me too seriously, I'm being a little silly in bringing this up. What if Y isn't missing an "arm," but is in reality missing a "rib"... lol. Mar 13 05, 8:23 PM

TheAlphaWolf

some of your body parts are not only junk but they're bad for you. Wisdom teeth for example. You don't need wisdom teeth and they cause a lot of problems. Erector pili are also useless. There's no use in raising your hair. heck... you can't even raise the hair on your head and you still have erector pili there. There are even things in SOME people and not in others, like neck vertebrae (like reptiles), extra ribs (like apes?), a muscle in your groin (like marsupials), the ability to roll your tongue, ear wagging muscles, etc, etc, etc. Just because one or two body parts were once thought to be useless and are later found that they weren't doesn't mean that all useless body parts are useful in some way. Mar 13 05, 8:32 PM

TheAlphaWolf

and those are the things just out of the top of my head! the lunula or however you call it in some people's nails is obviously useless since I don't have it, hair in many places is useless, there are dead end tubes in women that serve no purpose, etc. Mar 13 05, 8:35 PM

kaylofgorons

:) Goosebumps are funny. Just don't shave your legs if you have them--which I guess only applies to girls! A little variety in a species never hurts. I'm not going to argue with you; I'm in a good mood. I had wild cherry Pepsi yesterday, and was hyper all afternoon on the caffeine. My mood has yet to turn back to despair of homework. ACK! I'm being attacked by books! Noooo! Mar 13 05, 8:42 PM

TheAlphaWolf

the point is not if it doesn't hurt, but if it DOES anything. and the examples I gave you don't do anything. what the heck is the point of goosebumps? they're vestigial. useless. junk. What's the point of wisdom teeth? to hurt you? they're junk. and shaving your legs doesn't just apply to girls... swimmers shave their legs too :P Mar 13 05, 8:59 PM

lothruin

Eh, I don't think that superfluous structures are really genetic junk, Alpha. The "junk" I was referring to are pieces of genetic code whos' functionality have been undermined by mutation. If a bit of code is corrupt and/or unusable because of a mutation, it is genetic junk. Anything that still actually does something is not junk. It may not be beneficial, it may even be hurtful, but it isn't really junk. Mar 14 05, 1:22 PM

TheAlphaWolf

I know that but kay said "I highly doubt that much of our genetic code is "junk". Certain very important parts of my anatomy were once considered "junk". Doctors now refuse to remove tonsils when a few decades ago nearly everyone had their tonsils out. We're just starting to understand DNA--give them a few more years..." so I was responding to that. Mar 14 05, 6:36 PM

kaylofgorons

rofl...lol. Mar 14 05, 8:27 PM

lothruin

I know, and MY point is, all the things you cited as "vestigal" and useless are probably still not "junk". The only real junk in our DNA is actual useless code. Code that doesn't even make a useless bit of anatomy, but does absolutely nothing instead. Mar 14 05, 8:28 PM

TheAlphaWolf

and MY point was that I wasn't talking about DNA at all! lol. I know that if DNA codes for something (anything) it's not junk. Mar 15 05, 7:10 PM

lothruin

Well, if you consider wisdom teeth to be "junk" then why wouldn't you consider the DNA associated with wisdom teeth to be junk? And I would argue that wisdom teeth aren't REALLY junk either. Mar 16 05, 6:15 PM

TheAlphaWolf

because if a piece of DNA codes for any protein, it's not junk. junk DNA is the DNA that doesn't code for anything. I'm guessing they have tried to make GM bacteria or something with junk DNA and found out that it didn't code for anything. so... if wisdom teeth aren't junk, what do you call an unecessary thing that causes problems? humans' jaws are naturally too small even for regular teeth. a person having perfectly straight teeth (naturally) is extreamely rare because all the teeth just don't fit how they're supposed to. other animals have perfectly straight teeth. (but I am not in any way even kind of maybe suggesting that teeth are vestigial! I'm just making my case that we don't need four other extra molars there) Mar 16 05, 8:05 PM

TheAlphaWolf

in other words, the DNA itself isn't junk. it's the thing that the DNA codes for that is. Mar 16 05, 8:07 PM

TheAlphaWolf

argh. Sorry for the triple post but I know someone will misunderstand me. I'm not saying that some DNA isn't junk, I'm just saying that the DNA that codes for the junk is not junk because it codes for something. We have plenty of junk DNA though. Mar 16 05, 8:10 PM

kaylofgorons

Lol, isn't this where you say the next stage of human evolution is either to eliminate wisdom teeth or to have bigger jaws? Mar 16 05, 8:53 PM

TheAlphaWolf

actually no because it doesn't interfere with sex. Mar 16 05, 9:46 PM

kaylofgorons

O_o So you're saying we're stuck with crooked teeth and annoying wisdom teeth? Man... Mar 16 05, 9:53 PM

TheAlphaWolf

yep. It dosen't interfere with your ability to have offspring so there's no selection of the genes. Mar 17 05, 6:45 PM