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Re: Transposable elements??


>Moreover I dont see how chromosome loss or transposable elements are 
>fitted in with  your opinion that yellow is supposed to be 
>chloroplast encoded!!!?

I NEVER said, nor did I imply that yellow hostas were due to 
chloroplast genes!  Therefore YOU are starting out with a wrong 

>It must be remembered that yellow plants in hosta are always 
>heterozygous for green and nulear encoded so a simple mit rec gives a 
>green edge

Yes, and a loss of a piece of chromosome that carries the Y gene 
leaves the plant in the null state for that gene.  Without the Y gene 
the cells are then green because only the y gene is present.  Thus, 
chromosome loss is just as reasonable explination for yellow hostas 
developing green edges as is mitotic recombination, and actually much 
more feasible of an explination.  Also, transposible elements is more 
likely a good explination then is mitotic recombination because 
transposible elememnts are involved in the development of many forms 
of variegation, for example in streaked flowers such as Morning Glory. 

The problem you have Ben is that you are making an assumption that 
mitotic recombination IS the cause of gren edges on yellow hostas.  
While this is a possibility, you have not proven it and there are 
other explinations that are just as good, if not better.

The problem with mitotic recombination is that you can't easily test 
the segerating daughter cells.  If you want to prove that mitotic 
recombination is responsible for green edges on yellow hostas, then 
you will need some marker genes on the same chromosome arm as the Y 
gene and then analyze the genotype of the resulting daughter cells.  
In yeast and other single cell organisms this isn't that difficult to 
do, but even there you have to set up special screening tests to 
detect the recombinants because the rate is so low, and that is even 
with the use of high irriadation doses.  

Now, it is possible to do some analysis of hostas to see if mitotic 
recombination may be a possible cause of green edges, but without good 
marker genes on the same chromosome are as the Y gene is on, you just 
won't have the proof you need.

>It again shows that it is easy to apply the wrong thing Both 
>chromosome loss and especially transposible elements are very 
>rare phenomena, written about a lot because it is interesting, not 
>because it is common.

Are you being arrogant or ignorant?  Have you ever read a book on 
plant cytology and cytogenetics?  Chromosome loss is VERY common.  
Have you not heard of aneuploid plants?  Pieces of chromosomes get 
lost, translocated, inverted and what have you quite often.  With 60 
chromosomes in hostas that are not easy to distinguish, it would be 
easy for a piece of chromosme to break off and difficult to see it 
under a microscope.  As to transposible elements, I suggest you go to 
amazon.com's book section and search for books on transposible 
elements and for books on mitotic recombination and tell me which is 
more important!  There is a LOT of research interest in transposible 
elements right now and I doubt that you will find anyone working on a 
grant on mitotic recombination.  When is the last time someone won a 
Nobel Prize for work on mitotic recombination!  

Actually, there is evidence that mitotic recombination is NOT a cause 
of green edges on yellow hostas.  If you propagate Fascination you 
will eventulally get an all green form.  It makes a decent landscape 
plant for general gardeners.  However, you will also notice that some 
of those green formed Fascinations will revert back to the streaked 
form.  If I follow your argument, the all green fascination would have 
to be genotype yy, but yet it is capable of developing yellow 
streaking, which should require the dominate Y allele.  So now, are 
you going to say that all these green Fascinations that revert back to 
streaked are due to a mutation of "y" to "Y"?  

>>Ben, almost any good example of mitotic recombination in higher 
>>plants IS news! 
>Maybe for you, not for a geneticist who reads the litterature

Please Ben, would you give me ONE good example of mitotic 
recombination in a higher plant (not hostas) that did not involve high 
doses of irriadiation or extremely contrived experimental conditions? 
And since you seem to imply that you do read the litterature, would 
you please provide us with a biography of articles of mitotic 
recombination in HIGHER plants so that we can all bring ourselves up 
to your level of knowledge.  I know you can find some references to 
mitotic recombination in yeast and fungi, but we are interested in 
higher plants!  I've been searching for all these references you imply 
exists for mitotic recombination in higher plants and I just can't 
find them.  IF they exist I certainly would like to read them.

Joe Halinar

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