[DD.]

Have a look at this previous thread on the subject, should explain all..

http://www.chat.allotment-garden.org/viewtopic.php?p=316013&highlight=parent*#316013

[Trillium]

To add to this, you don't always know who the parents were  of the F1's. Frequently, neither parent on its own is desireable, but a cross makes something worthwhile. I had some F1 cherry toms go to seed and sprout on me so I let them grow to see what I got....the worst tasting tom I've ever had, yet the hybrid itself is very delicious and sweet. One extra factor is that when the hybrid is pollinated, you'll get yet another variety in the mix as its unlikely you're already growing the 2 original parents, so now you've got something totally different to the original with no hope of return.

[Aunt Sally]

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookgenintro.html

Scroll down to the diagrams.

They use big S (dominant characteristic) and little s (recessive characteristic) as the genes demonstrating the hybridisation - wrinkly and smooth peas.

The first cross of the parent plants produces the F1 generation

Crossing the F1 generation produces the F2 generation

[DD.]

Ah - it's all clear now!

[Aunt Sally]

You should know all about peas Dave  

[DD.]

You should know all about peas Dave  

I do, they're green, round and have coloured bits on the end at this time of year.

[Aunt Sally]

    So I see  

[pushrod]

I know that they are right in that keeping seeds from this plant will not produce a similar F1 plant but what I can't understand is why not.  Can anyone explain, in simple terms, as to why they do not come true to their parent?  :?

F1's in these cases are bred from pure breeding plants of two different types. The pollination process is fiddly and will usually involve the flowers of one of the  parent plants having its stamens removed to prevent self pollination. Hence the expense. The fruit produced is harvested and the seed collected. As they have come from 2 pure breeding parents their genes are a mixture. When they come to produce their own sex cells (eggs and pollen) you can not tell which of the genes will end up in them - it is what is called "a random assortment". Pure breeding plants have identical pairs of genes and so when their pairs divide to produce the sex cells they all get similar genes.
If you think of 2 pedigree labradors breeding -all their pups will look like labradors (they are pure breeding) . If however two mongrel dogs mate you could get 6 totally different looking puppies.
If you mated say a pure labrador with a pure yorkshire terrier all the puppies would be very similar (the F1) but if you mated these puppies together when they were older you would get all sorts from them (these would be the F2). IE the F1 do not come true but will be a right old mix.
 Hope you understand this. If you want to understand it technically you will need some understanding of meiosis and terms like heterozygous , homozygous etc.