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Life Sciences => Cells, Microbes & Viruses => Topic started by: alastair84 on 12/05/2004 18:41:02

Title: lyonisation, quick Question
Post by: alastair84 on 12/05/2004 18:41:02
i understand lyonisation is the process of random X chromosome inactivation in a famale, which involves methylation of certian parts of one of the X chromosomes.
Just a quick question:
Does lyonisation affect ALL the cells in the female?
e.g. do some cells escape lyonisation and have both X chromosomes active?
Title: Re: lyonisation, quick Question
Post by: Rokitansky on 12/05/2004 18:54:11
Sincerly, i don`t know. But, what i do know, is that there are parts of X chromosome which are not inactivated. These genes have their own locuses on the short part of Y chromosome also (in males), and these are called pseudoautosomic genes.
Title: Re: lyonisation, quick Question
Post by: alastair84 on 12/05/2004 19:00:58
yes, of course. Logical thinking would determine this, because if ALL of the genes of one of the X Xsomes were inactivated, then the female would effectively have Turners Syndrome, which results from genotype of 45, X0
Title: Re: lyonisation, quick Question
Post by: alastair84 on 12/05/2004 19:02:59
actually from the above reasoning, one could assume that ALL cells in the female DO undergo lyonisation, otherwise the female may have symptoms of 47, XXX??? this is some dodgy reasoning from me, lol.
Title: Re: lyonisation, quick Question
Post by: Rokitansky on 12/05/2004 22:17:32
quote:
Originally posted by alastair84

actually from the above reasoning, one could assume that ALL cells in the female DO undergo lyonisation, otherwise the female may have symptoms of 47, XXX??? this is some dodgy reasoning from me, lol.


well, no. Symptoms in 47,XXX are due to genes in those pseudoautosomic loci are in excess. In this female, both X chromosomes are inactivated.
I was thinking through this and it could have been a reactivation of second X chromosome before mejotic division in gonads take place, but functional significance of this is unclear to me.
Title: Re: lyonisation, quick Question
Post by: alastair84 on 12/05/2004 22:46:18
thanks. I have researched a little more and think the answer to the original question is yes, all cells undergo lyonisation, well that's what i'm going to put down in my exams coming up anyway.
Title: Re: lyonisation, quick Question
Post by: Rokitansky on 12/05/2004 23:21:16
good luck !
Title: Re: lyonisation, quick Question
Post by: chris on 13/05/2004 03:16:12
The question of Lyonisation was discussed in a previous topic, here's the link :

http://nakedscientists.com/forum/topic.asp?TOPIC_ID=793&whichpage=1

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx
Title: Re: lyonisation, quick Question
Post by: MayoFlyFarmer on 13/05/2004 07:07:51
quick answer = yes

That's no moon.... its a GRAPEFRUIT!!!!
Title: Re: lyonisation, quick Question
Post by: MayoFlyFarmer on 13/05/2004 07:08:23
well i guess there are exceptions to every rule, but i can't think of any and I assume you just meant in general

That's no moon.... its a GRAPEFRUIT!!!!