dh321 at excite.com
Fri Sep 21 00:06:42 EST 2001
I don't know why the snapdragon experiment doesn't work. In Mendel's
peas, the starch grain shape in smooth peas is different between
hetereozygotes (Rr) and homozygotes (RR) but the smooth pea seeds all
look the same macroscopically. There might also be detectable
differences in the sugar content. Maybe try improved disease resistant
cultivars versus unimproved susceptible cultivars or high vitamin
cultivars versus regular cultivars. Male and female individuals of the
same species often appear the same when out of flower but are
obviously different when in flower.
If you grew dwarf and normal cultivars of peas or corn and sprayed the
dwarfs with gibberellic acid, you would have two normal-size plants
but with two different genotypes. You could have the unsprayed dwarf
plant as a control to show the genetic difference.
Probably you will find some suitable plants pairs among all the
various mutants of Arabidopsis and Wisconsin Fast Plants. There is a
mutant Arabidopsis low in ascorbic acid which is very susceptible to
ozone, sulfur dioxide and ultraviolet B radiation compared to normal
B.T.Meatyard at warwick.ac.uk (Barry Meatyard) wrote in message news:<firstname.lastname@example.org>...
> Dear All,
> I have tried unsuccessfully over the years to demonstrate biosynthetic
> pathways leading to colour production in Antirrhinum flowers. The principle
> is that white flowers are white because the biosynthetic pathway leading to
> anthocyanidin production is blocked in one of 2 genes determining enzymes
> in the pathway. The blocking gene can be identified by the addition of a
> flavonol intermediate (dihydroquercetin) to an excised white flower via its
> stalk. If the flower subsequently develops colour the block is in the 2nd
> gene, if it fails to produce colour the block is in the first gene.
> That's the story (according to June New, J.Biol.Ed (1986) 20 p229-230) but
> I've never managed to get it to work and I haven't been able to contact
> June New to see if there are tricks of the trade that aren't apparent in
> the article.
> The reason for doing this is to demonstrate to students that white flowers
> may be white for more than one reason and thus represent biodiversity that
> cannot be observed simply by looking at the outward phenotype.
> I've used dihydroquercetin from Sigma, but since no chemical formula was
> given in the paper it may be that the name covers more than one structure
> and I'm not discounting having the wrong 'dihydroquercetin'!
> Can anyone throw any light on this or suggest alternatives that would
> enable differences between apparently similar plants to be visualised in
> such a way (without resorting to DNA technology)? I want this to be simple
> and effective enough to be usable in high schools in UK.
> Any suggestions or advice welcome.
> Many thanks,
> Dr.Barry Meatyard
> Environmental Sciences Research and Education Unit
> Warwick Institute of Education
> University of Warwick
> CV4 7AL
> Email: barry.meatyard at warwick.ac.uk
> Tel: 44 (0) 2476 524228
> Fax: 44 (0) 2476 523237
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