Date: Wed, 18 Oct 2000 16:07:02 +0000 From: jan.schlauer@uni-tuebingen.de To: cp@opus.hpl.hp.com Message-Id: <aabcdefg3002$foo@default> Subject: Re: _Drosera_ hybrids
Dear Miguel,
> Unless I am misinformed, aneuploidy, as a form of polyploidy, refers only
> to the presence of extra single chromosomes, as opposed to auto- and
> allo-polyploidy, which refer to the multiplication of entire genomes.
You are right. Aneuploidy is, however, sometimes also used (rather
incorrectly, I admit) to include all chromosome counts that lead to
problems during meiosis.
> When we cross D. rotundifolia (a diploid?) with D. intermedia (diploid
> too?) we do get an infertile hybrid, as chromosomes in the diploid
> offspring cannot find clear homologues to pair with.
Did you really do this experiment, and were the parents identified
correctly?
> However, were we to
> double the chromosome number, we would find a situation in which
> chromosomes can pair up with the extra copies of themselves, producing
> bivalents which separate correctly at meiosis.
dto.?
> When you state D. rotundifolia and D. anglica have different ploidies,
> which is the polyploid?
_D. anglica_. It is tetraploid.
> If we were to cross diploid with tetraploid, the
> resulting offspring would be triploid, and triploids are generally
> infertile (but rarely sterile).
Correct.
> However, I think aneuploid offspring don't arise normally just from
> crossing parents with different ploidies, or different diploid chromosome
> numbers.
This depends on the definition used for aneuploidy. I agree that in
the case of _D. rotundifolia * D. anglica_ the offspring should
rather be called triploid.
Kind regards
Jan
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