Re: Re: Dusky Challenger
- Subject: Re: [iris-talk] Re: Dusky Challenger
- From: a*@cs.com
- Date: Wed, 26 Dec 2001 14:04:01 EST
In a message dated 12/26/01 7:48:16 AM Mountain Standard Time,
ehenon@earthlink.net writes:
> I am very excited about the book "The World of Irises" that Santa
> brought for Christmas. Unfortunately, the genetics chapter went over
> my head. The lesson regarding the characteristics of diploids and
> tetraploids is beyond my grasp. I understand that Snow Flurry was a
> breakthrough but I am not sure I understand what happened in the
> hybridization process that resulted in Snow Flurry. Can someone
> explain in easy-to-understand terms?
A brief account is presented on page 62 of TWOI. Its pod parent, PURRISSIMA,
was tetraploid. Its pollen parent, THAIS, was diploid. Crosses like this
contributed signifiantly to the development of our modern tetraploid TBs, but
the offspring are typically triploids. Once in a while, however, an
unreduced gamete results in a tetraploid offspring like SNOW FLURRY.
There's a diagram of meiosis on page 379, which shows how haploid cells are
normally produced from a diploid cell. If the Second Cellular Division
doesn't occur as shown, the result is an unreduced gamete that has twice as
many chromosomes as usual.
The atypical two sets of chromosomes from its diploid parent, added to the
two sets from its tetraploid parent, made SNOW FLURRY a "breakthrough"
tetraploid in the sense that it broke a fertility barrier.
Sharon McAllister
[Non-text portions of this message have been removed]
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