Barr body

[Mstoothlady2012]

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Barr body = inactive X chromosome

Cliffs says that most of the genes in inactive X chromosome are not expressed nor do they interact in a dominant/recessive or codominant manner with their respective alleles on the x chromosome that is expressed.

So basically this means most of the time only 1 X controls all the gene activity in females right? Isn't this just like male having 1 X? So for example when male has only 1 recessive allele for hemophilia, his phenotype is hemophillic because there is no other X. So shouldn't this be true for females as well? Coz even if other X (inactive) had dominant trait of hemophilia, it would still not express it since that X is inactive. Then why doesnt female with Xh on active chromosome and XH on inactive chromosome called hemophillic?

I am missing something here, can't figure out what though 😕

Thanks!

 

[Mstoothlady2012]

Lol nvm Cliffs has the exact same example that I said like 2 paragraphs down

 

[Colos]

hey...just trying to remember this from my genetics class, but although the x chromosome may be 'inactive' in females it still contains necessary genetic information for the female, so it's not just useless.
So, the line that says 1 gene contols all activity, I would have to think is not completely correct there.
For the male, he only has the single x chromosome and thus must represent that trait.

 

[Mstoothlady2012]

hey...just trying to remember this from my genetics class, but although the x chromosome may be 'inactive' in females it still contains necessary genetic information for the female, so it's not just useless.
So, the line that says 1 gene contols all activity, I would have to think is not completely correct there.
For the male, he only has the single x chromosome and thus must represent that trait.

Yes the inactive X has the same genes as the active X but most of the genes are turned off. So there is a possibility of turning off the dominant trait. In that case the female with genotype Xh XH could be hemophillic.

 

[Mstoothlady2012]

One more question...

what happens when this inactive X is inherited by a son?

 

[Mstoothlady2012]

WOW no1 can help me out?

 

[osimsDDS]

One more question...

what happens when this inactive X is inherited by a son?

uhhmm X inactivation i think only happens when you have 2 X's, if you have only 1 X like in a male then there is no X inactivation, therefore it only occurs in females i believe

 

[DRHOYA]

One more question...

what happens when this inactive X is inherited by a son?

If for instance (from your above example), there is the hemophiliac allele on the inactive X chromosome given to the son, then I would think that the son would not express the gene, since it is on the inactice X. This is a very good question though. Hmm, now to think about it, are Albino's classified as having inactive chromosomes. Ex: A male with inactive-X Y could be albino, due to lacking all the maternal traits passed along??

 

[harrygt]

The inactive X will be activated in the son. The X of every male individual is going to be ACTIVE no matter if it was an inactive X before.
Regarding solving the genetic problems, Ignore the inactivation process. I know this is confusing, and in fact it is much more complex in real word. The genetic problems that we get on DAT [and most BIO tests] are ignoring the inactivation process. I hope this helps. (BTW, I just got a 21 on CDP test #6] SO happy😀

 

[Mstoothlady2012]

uhhmm X inactivation i think only happens when you have 2 X's, if you have only 1 X like in a male then there is no X inactivation, therefore it only occurs in females i believe

yea I know X-inactivation only happens in females but I was wandering what happens when this female passes on her inactive X to the son.

 

[Mstoothlady2012]

If for instance (from your above example), there is the hemophiliac allele on the inactive X chromosome given to the son, then I would think that the son would not express the gene, since it is on the inactice X. This is a very good question though. Hmm, now to think about it, are Albino's classified as having inactive chromosomes. Ex: A male with inactive-X Y could be albino, due to lacking all the maternal traits passed along??

I am confused by your example. Albino is also X-linked recessive right? So it means if the son gets inactive X from the mother then he won't be albino.

 

[osimsDDS]

yea I know X-inactivation only happens in females but I was wandering what happens when this female passes on her inactive X to the son.

gets activated...because males are hemizygous (only 1 X chromosome), my bad didnt realize you knew that

 

[Mstoothlady2012]

The inactive X will be activated in the son. The X of every male individual is going to be ACTIVE no matter if it was an inactive X before.
Regarding solving the genetic problems, Ignore the inactivation process. I know this is confusing, and in fact it is much more complex in real word. The genetic problems that we get on DAT [and most BIO tests] are ignoring the inactivation process. I hope this helps. (BTW, I just got a 21 on CDP test #6] SO happy😀

yea harry what you are saying makes sense. The X has to get activated again b/c X chromosome carries some very important genes, which are also required my male and Y doesn't carry those genes (If I remember correctly from genetics).

Damn first 20 and now 21. I have to take #5 and bit your 20 in that and then I will bit your 21. Bring it on!! Lol its funny how you started scoring high after I told you that I broke the curse of 18!! Its like I challanged you or something - So competitive harry 🙄

 

[DRHOYA]

I am confused by your example. Albino is also X-linked recessive right? So it means if the son gets inactive X from the mother then he won't be albino.

Sorry. Disregard my example, as obviously if the inactivated X in a female is passed to male offspring, then it would have to be activated because males only have 1 X.


Harry. Nice job man!

 

[shoombol tallah]

yea harry what you are saying makes sense. The X has to get activated again b/c X chromosome carries some very important genes, which are also required my male and Y doesn't carry those genes (If I remember correctly from genetics).

Damn first 20 and now 21. I have to take #5 and bit your 20 in that and then I will bit your 21. Bring it on!! Lol its funny how you started scoring high after I told you that I broke the curse of 18!! Its like I challanged you or something - So competitive harry 🙄

I cant beat that stupid curse. I took test number 7 today and yup 18 again!! 1-7 have all been 18 , is that like my limit or something. Anyways does anyone have a really good trick for the angles? I get 11-15 on most sections but i cant do well on angles. Plus it kills my timing because i spend so much time looking at them. Ive tried the nose, hill, hold your marker up trick and i cant seem to consistently get them right. Any advice ?

 

[Mstoothlady2012]

The inactive X will be activated in the son. The X of every male individual is going to be ACTIVE no matter if it was an inactive X before.
Regarding solving the genetic problems, Ignore the inactivation process. I know this is confusing, and in fact it is much more complex in real word. The genetic problems that we get on DAT [and most BIO tests] are ignoring the inactivation process. I hope this helps. (BTW, I just got a 21 on CDP test #6] SO happy😀

Guess what? guess what? I got 21 on # 5 oh yeaa!! Sorry Harry I bit you again 😀 You were right though...easiest test of all especially the pattern folding ...i have never gotten 100% on pattern before on CDP lol

 

[Mstoothlady2012]

I cant beat that stupid curse. I took test number 7 today and yup 18 again!! 1-7 have all been 18 , is that like my limit or something. Anyways does anyone have a really good trick for the angles? I get 11-15 on most sections but i cant do well on angles. Plus it kills my timing because i spend so much time looking at them. Ive tried the nose, hill, hold your marker up trick and i cant seem to consistently get them right. Any advice ?

For angles always always always go with your first instinct!! if you keep on looking at the answer choices you are really gonna confuse yourself

1) Never try to eliminate answer choices just by looking at the #s!!!!

for eg. a) 1,2,3,4
b) 2,4,1,3
c) 1,3,4,2
d) 1,3,4,2

These answer choices make you feel like 1 is definitely the smallest angle, but that is not true! CDP tries to trick with these type of answer choices. I don't know if you do this or not, but i used to do this a lot before lol

2) Try to figure out your own sequence by writing it down on your sheet and then pick you answer. This use to take up alot of time for me so I stopped doing it once I got into the groove.

3) Definitely do look at the choices first and look at the smallest angle choices so you can compare only those angles and pick the best choices and then move on. You can do the same for the largest angles as well.

for eg. a) 2,3,1,4
b) 3,2,1,4
c) 2,1,4,3
d) 3,1,2,4

So now you know for sure that the smallest angle is either 2 or 3 so just look at those angles and figure out which one is smaller. LEts say you pick 2 so now you can eliminate b &d. Next look at the largest angle choices, you have two choices 3 or 4. Figure out which one is largest and you get your answer. Sometimes if you don't get answer just by these two then you can atleast eliminate 50% of your choices.

4) I mentioned this in other thread but again for angles less than ~100 degrees you can tilt your head back a little (increase the distance between you and the computer), which will help you visualize the angles better.

5) Also you can think about the angles like this, which angle would fit into which one?Again this works best for the small angles, less than 100 degrees or so. Sorry I suck at those large angles which are like 160 degrees, I dont have any tricks for those.

I hope this helps! I tried to explain but its so hard to explain these things in words.

 

[Mstoothlady2012]

Oh and I am not genius at angles I get around 10-11, but these are some of the things that I do which helps. You might already know it but thought I had post it anyways 😀

 

[Deontologist]

Damn first 20 and now 21. I have to take #5 and bit your 20 in that and then I will bit your 21. Bring it on!! Lol its funny how you started scoring high after I told you that I broke the curse of 18!! Its like I challanged you or something - So competitive harry 🙄

What is CDP ...just curious......?? never heard of it before....!!

 

[DRHOYA]

Hahaha. Yeah the angles are the toughest and most variable section. I guess the more practice the better. Just warning you guys, the angles on like tests 7-9 are insane.

Btw, I have you both beat on test 5😛🙂.
See, Crack can be fun.

 

[Mstoothlady2012]

Hahaha. Yeah the angles are the toughest and most variable section. I guess the more practice the better. Just warning you guys, the angles on like tests 7-9 are insane.

Btw, I have you both beat on test 5😛🙂.
See, Crack can be fun.

Lol what'd you get?

 

[DRHOYA]

Lol what'd you get?

It was insane, a 28. I only missed 2 angle questions.

 

[Mstoothlady2012]

It was insane, a 28. I only missed 2 angle questions.

Overall was 28 😱

 

[Mstoothlady2012]

What is CDP ...just curious......?? never heard of it before....!!

Crack DAT PAT

 

[shoombol tallah]

For angles always always always go with your first instinct!! if you keep on looking at the answer choices you are really gonna confuse yourself

1) Never try to eliminate answer choices just by looking at the #s!!!!

for eg. a) 1,2,3,4
b) 2,4,1,3
c) 1,3,4,2
d) 1,3,4,2

These answer choices make you feel like 1 is definitely the smallest angle, but that is not true! CDP tries to trick with these type of answer choices. I don't know if you do this or not, but i used to do this a lot before lol

2) Try to figure out your own sequence by writing it down on your sheet and then pick you answer. This use to take up alot of time for me so I stopped doing it once I got into the groove.

3) Definitely do look at the choices first and look at the smallest angle choices so you can compare only those angles and pick the best choices and then move on. You can do the same for the largest angles as well.

for eg. a) 2,3,1,4
b) 3,2,1,4
c) 2,1,4,3
d) 3,1,2,4

So now you know for sure that the smallest angle is either 2 or 3 so just look at those angles and figure out which one is smaller. LEts say you pick 2 so now you can eliminate b &d. Next look at the largest angle choices, you have two choices 3 or 4. Figure out which one is largest and you get your answer. Sometimes if you don't get answer just by these two then you can atleast eliminate 50% of your choices.

4) I mentioned this in other thread but again for angles less than ~100 degrees you can tilt your head back a little (increase the distance between you and the computer), which will help you visualize the angles better.

5) Also you can think about the angles like this, which angle would fit into which one?Again this works best for the small angles, less than 100 degrees or so. Sorry I suck at those large angles which are like 160 degrees, I dont have any tricks for those.

I hope this helps! I tried to explain but its so hard to explain these things in words.

cool thanks ms toothlady i'll give it a try and see how it works 👍

 

[harrygt]

I finally got back to my laptop. I see, you cracked my 20 on test 5. You are so mean misstoothy.😉

 

[HoangDDS]

uhhmm X inactivation i think only happens when you have 2 X's, if you have only 1 X like in a male then there is no X inactivation, therefore it only occurs in females i believe

100% right. X inactivation only occurs in females. This is done to control over expression of X proteins. One X chromosome is inactivated early in development to equalize the expression of X-linked genes in the two sexes. The X that is chosen to get inactivated is completely random between two normal X. However with abnormal X or an X;autosome translocation (still considered abnormal) it is usually the abnormal X that is inactivated. Inactived X becomes the Barr body in interphase nuclei.

Also Colos was right too. There is about 10-15% of the inactivated X genes that escapes inactivation.

You do not need to know this but it explains why inactive X that is passed on to the son is activated -- there is an XIST gene on the XIC (X inactivation center) that makes an X inactive in the presence of two X. That is why son's X are not inactive.

lol, I can't believe this turned into a Crack PAT tutorial.

 

[tncekm]

100% right. X inactivation only occurs in females. This is done to control over expression of X proteins. One X chromosome is inactivated early in development to equalize the expression of X-linked genes in the two sexes. The X that is chosen to get inactivated is completely random between two normal X. However with abnormal X or an X;autosome translocation (still considered abnormal) it is usually the abnormal X that is inactivated. Inactived X becomes the Barr body in interphase nuclei.

Also Colos was right too. There is about 10-15% of the inactivated X genes that escapes inactivation.

You do not need to know this but it explains why inactive X that is passed on to the son is activated -- there is an XIST gene on the XIC (X inactivation center) that makes an X inactive in the presence of two X. That is why son's X are not inactive.

lol, I can't believe this turned into a Crack PAT tutorial.

Great post right here.

I feel the need to clarify one point, however, because it makes sense of some things. When HoangDDS says that which X chromosome is inactivated (turns into a barr body) is completely random, that means that literally 50% of each of the two X chromosomes in the body is in barr body form. This takes care of msot dominant/recessive questions I've seen with barr body X chromosomes.

 

[Mstoothlady2012]

100% right. X inactivation only occurs in females. This is done to control over expression of X proteins. One X chromosome is inactivated early in development to equalize the expression of X-linked genes in the two sexes. The X that is chosen to get inactivated is completely random between two normal X. However with abnormal X or an X;autosome translocation (still considered abnormal) it is usually the abnormal X that is inactivated. Inactived X becomes the Barr body in interphase nuclei.

Also Colos was right too. There is about 10-15% of the inactivated X genes that escapes inactivation.

You do not need to know this but it explains why inactive X that is passed on to the son is activated -- there is an XIST gene on the XIC (X inactivation center) that makes an X inactive in the presence of two X. That is why son's X are not inactive.

lol, I can't believe this turned into a Crack PAT tutorial.

Are you sure about this? Coz Cliffs says and I quote

" When X-inactivation beings, one of the two chromosomes in each embryonic cell randomly and independently becomes inactive. Subsequent daughter cells will have the same X chromosome inactivated as did the embryonic parent cell from which they originated. "

I feel like these 2 sentences contradicts each other. First it says random and then it says that its pre-determined which one will be inactivated. I guess I am thinking too into it....but I am trying to apply the knowledge like DAT wants us to do 😎😀

Thanks!

 

[HoangDDS]

Are you sure about this? Coz Cliffs says and I quote

" When X-inactivation beings, one of the two chromosomes in each embryonic cell randomly and independently becomes inactive. Subsequent daughter cells will have the same X chromosome inactivated as did the embryonic parent cell from which they originated. "

I feel like these 2 sentences contradicts each other. First it says random and then it says that its pre-determined which one will be inactivated. I guess I am thinking too into it....but I am trying to apply the knowledge like DAT wants us to do 😎😀

Thanks!

I am absolutely postively sure about that. I even double checked my human genetics notebook, which I just took last semester, which I why I was so eager to input on your thread. One normal X will be inactivated randomly between two normal Xs. Between one normal and one abnormal X, the abnormal X usually becomes inactivated. And when this does not happen (due to mutation at the XIST gene), then females will have abnormal phenotype.

And you right, we shouldn't worry too much about the super details off all of this. I guess, just understand X inactivation occurs in females only.

 

[Mstoothlady2012]

I am absolutely postively sure about that. I even double checked my human genetics notebook, which I just took last semester, which I why I was so eager to input on your thread. One normal X will be inactivated randomly between two normal Xs. Between one normal and one abnormal X, the abnormal X usually becomes inactivated. And when this does not happen (due to mutation at the XIST gene), then females will have abnormal phenotype.

And you right, we shouldn't worry too much about the super details off all of this. I guess, just understand X inactivation occurs in females only.

Thanks! yea you are right all i have learn in my genetics and other bio classes is barr body = X inactivation. None of them have gone into much detail that's why i am having hard time answering my own questions. I will just let it go...thanks again! 🙂