Re: _Drosera_ hybrids

From: jan.schlauer@uni-tuebingen.de
Date: Wed Oct 18 2000 - 09:07:02 PDT


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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