why no 28S RNA?

Joseph C. Bagshaw jbagshaw at wpi.edu
Mon Dec 28 12:34:34 EST 1998

I tried to respond to this inquiry a few days ago, but my message did not
get through, so I'll try again.

In Drosophila and many other insects, the 28S molecule contains a cryptic
nick very close to the center.  Under denaturing conditions the 28S falls
apart into two pieces that are usually indistiguishable from the 18S on a
gel.  The same is true for crustacea that I have tried, including
Artemia, Penaeus and Macrobrachium, so I would not be surprised if it
occurs in an annelid, one of the suspected ancestors of crustacea.

********************  HAVE GENES, WILL TRAVEL  ********************
Joe Bagshaw, Worcester Polytechnic Institute
jbagshaw at wpi.edu
Roadkill on the information superhighway.

On 23 Dec 1998, Narayanan Karthikeyan wrote:

> > 
> > Dear netters,
> > 
> > I have made total RNAs from earthworm for many many times, 
> > but only got 18S band on agarose gel, no 28S band at all. I 
> > could get 28S and 18S RNAs with other materials such as fish 
> > egges and chiken liver. It doesn't like being digested by 
> > RNase, because the 18S band was very sharp and small band 
> > down the gel was not much . I have been trying with many 
> > protocals including Promega's total RNA isolation system 
> > using Guanidine thiocyanate, PerSeptive's purification kit 
> > using Proteinase K and the method combining phenol 
> > extraction and LiCl precipitaion. What ever a protocal I 
> > used the results were almost the same, e.g. no 28S RNA. I 
> > have got tired, it seems no hope for getting 28S RNA with 
> > earthworm. I really need help. Why is that? Any suggestions, 
> > ideas and hints will be appreiciated. 
> > 
> > Thanks in advance!
> > 
> > Tianyu
> > E-mail:jing at nic.hbu.edu.cn
> Hi:
> I also wondered the same when I was working with Drosophila system. I
> used to extract RNAs from Drosophila embryos and cell lines and found to
> have only one band around 18S. I have no idea why it is like that. But
> all my RNAs worked great for PCR and Northerns. So do not panic.
> If anyone got the reason for this phenomenon please let us know.
> Good luck
> Karthi

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