molecular arrangement of an inversion
psl...@yahoo.com
reintegrate.
My problem is that if you turn the piece 180 degrees 5' becomes 3' and
vice versa. does the information bearing strand switch strand when
it's reattached ? Or can a strand have a part that is arranged in the
opposite 3' to 5' direction?
If the inverted piece actually IS attached to the "other" strand, how
does the transcription process know to change strand for the inverted
piece ?
Now if thats not a problem, does that mean that the only reason only
one strand (in eucariotes) is transcribed is because there doesnt
happen to be any promoters on the "wrong" strand.
Perplexed in Peoria
<psl...@yahoo.com> wrote in message news:g020ia$1su1$1...@darwin.ediacara.org...
>I cant find any explanation of how an inverted piece of dna is able to
> reintegrate.
> My problem is that if you turn the piece 180 degrees 5' becomes 3' and
> vice versa. does the information bearing strand switch strand when
> it's reattached ?
Yes.
> Or can a strand have a part that is arranged in the
> opposite 3' to 5' direction?
Not even sure what this might mean.
> If the inverted piece actually IS attached to the "other" strand, how
> does the transcription process know to change strand for the inverted
> piece ?
Typically, the inverted unit is larger than a transcription unit and contains
a transcription unit within it. You need to realize that the distinction
between the coding strand and the other strand is a *local* distinction
and that the distinction is independently made for each transcription
unit. Any two consecutive genes (assuming they are independently
transcribed) may be in the same order on the same strand or in
opposite order on alternate strands.
You also need to realize that most of a typical eukaryote genome is
'junk' and hence that both endpoints of the typical inversion are probably
in the junk untranscribed regions between genes.
> Now if thats not a problem, does that mean that the only reason only
> one strand (in eucariotes) is transcribed is because there doesnt
> happen to be any promoters on the "wrong" strand.
A better way of saying "only one strand is transcribed" is to say that
transcription units are scattered around the genome on both strands.
But any one transcription unit is on only one strand. Furthermore,
although theoretically it should be possible to have an overlap between
transcription units on opposite strands (so that in the area of overlap
both strands get transcribed) this doesn't seem to actually be the case
for any known genomes. Equally possible theoretically would be
overlapping transcription units on the same strand. This does seem
to happen sometimes, though it is usually described as having
'alternative transcription start sites' and 'alternative transcription stop
sites'.
Ron O
DNA is a double stranded molecule held together by hydrogen bonds.
The strands are antiparallel. One strand goes in the 5' to 3'
direction and the other strand goes in the 3' to 5' direction. You
can clip a piece out and invert it or put it back in, it doesn't
matter there are always matching ends to link to.
Google "DNA structure"
http://en.wikipedia.org/wiki/DNA
Transcription can go in either direction of any double strand of DNA.
The DNA template runs 3' to 5' and transcription of the matching RNA
goes from 5' to 3'.
Inversion will change the direction of transcription, but both strands
can be transcribed. Transcription is just the process of making RNA
from a DNA template. This can alter the regulation of genes that are
now found down stream of the inversion event.
Ron Okimoto
Graham Jones
Here's a picture to illustrate PiP's comments
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4.figgrp.973
Graham