Please help me understand tomato inheritance

[clkingtx]

Ok, I think I partially understand the filial generations, at least the meanings of F1, F2, etc. I understand that when you cross 2 open pollinated varieties, the F1s are all alike, producing identical plants, fruit, etc. The F2 generation varies widely, with the full range of characteristics of their "grandparents". I heard someone compare it to inheritance in humans, how children of the same parents are not identical, but vary widely. My question is, why is that not the case in the F1 generation? This is fascinating to me, and I want to learn more.
Thanks a lot,
Carrie

[Tom Wagner]

My question is, why is that not the case in the F1 generation? - Carrie

Tomatoes have perfect flowers meaning the flower's pollen and fruiting body is capable of pollinating itself. They can't happen with animals since they have different male and female parents in reproduction.

As people have eschewed marrying cousins from the same village as my grandparent's era did....people are almost like hybrids marrying hybrids. Their so-called F-1 children are more complicated than F-2. The best one could expect to imitate an F-2 family in people is for brother and sister to marry to create a sib mated F-2 offspring.

[clkingtx]

Ok, I understand. Thanks a lot!

[Darren Abbey]

The parental strains are homozygous for most genes, meaning they have two copies of the same version of each gene. Different parental strains will have different versions of many genes.

The F1 progeny will then have one copy of each version of each gene from each parent. All of the F1s will have the same genetics and so will be identical.

The F2 progeny get a random copy of each gene from each parent. Both F1s have two versions, so the F2s can get any combination of the versions for each gene. This generates a great deal of diversity.

[dice]

homozygous vs heterozygous is the key, and the fact that the offspring
need two copies of a gene, one from each parent, to be viable. The
copies can be identical, dominant-dominant or recessive-recessive, or
they can be different, dominant-recessive, but the seed still needs both
copies to grow.

Lets say one parent has dominant-dominant, which we will denote
as "AA". The other parent has recessive-recessive, which we will
denote as "aa". Both parents are homozygous for that gene pair,
but each has a pair that differs from the other's pair.

When they cross, all the offspring get an "A" gene from one parent
and an "a" gene from the other parent. So every F1 seed ends up
with an "Aa" gene pair for that gene, all the same.

When the F1 plant self-pollenates, it provides both genes of the gene
pair itself. For any given F2 seed, that seed can end up with "AA", "Aa,
"aA", or "aa" for that gene pair. ("Aa" and "aA" will produce the same
characteristics in the plant. The different ordering is an artifact of
writing systems rather than genetics.)

When you extend that "AA, Aa, or aa" possibility over all of the gene
pairs in the tomato genome, you get a lot of possible variations in
F2 plants that are not found in F1 plants if both parents had all
homozygous gene pairs (OP). If either parent had a lot of heterozygous
gene pairs (Aa, Bb, Cc, Dd, etc), then you can see that wide variation
in offspring in the F1 plants.

For some gene pairs there are no options. If the seed does not get
a matching gene pair for some metabolic functions, for example,
the plant does not survive. (Only AA is viable. Aa and aa are fatal to
the plant.) The differences we see in F? offspring are from the genes
where the plant can survive with AA, Aa, or aa gene pairs (and
BB, Bb, bb, CC, Cc, cc, etc).

[PNW_D]

A more visual explanation

http://kdcomm.net/~tomato/gene/genes.html

[Moshou]

As far as I know, about the dominant traits that will show up in the offspring of cross (first generation = F1), indeterminate growth is dominant, so is the red colour over yellow, RL over PL, etcetera

I am interested to learn more about 'etcetera'. Does anybody know which trait is dominant over the other?

[dice]

(Actually a plant with an Aa, Bb, Cc etc combo, even for a vital
metabolic function, would probably have AA, BB, CC behavior,
where the dominant gene is expressing itself in the plant. aa,bb,cc,
ie recessive-recessive, is where one more likely might find fatal
combinations that prevent the plant from growing into a mature
plant.)

[clkingtx]

Wow, so much good information! Thanks everybody!