understanding the genes and offsprings

[the gnome]

I just picked up sourbubble, probably BX4 seeds

can someone here devote the time to explain exactly what it means when I see seeds that are F2-F3 or a BX2-Bx3
I want to understand the relationships between them and what and where they are in the proverbial wood pile

 

[Tom Hill]

Hi TG,

Let a plant (Mexico) be called "P1".

Then, let another plant (Afghanistan) be called "P2".

OK then:

1) P1 x P2 = F1

2) F1 x F1 = F2

3) F2 x F2 = F3

4) etc, etc, etc

Then moving on to backcrossing (this should really be denoted as BC1, BC2, etc, instead of BX1, BX2 etc, but don't get hung-up on that).

One simple variation of backcrossing would be:

1) P1 x F1 = BC1

2) P1 x BC1 = BC2

3) P1 x BC2 = BC3

4) etc, etc, etc

 

[BrotherBuz]

^^^Thanks TomHill, I've always wondered about those abbreviation too. Now I know.

 

[the gnome]

my hats off to ya tom

that was very easy to digest.
now I understand why some seeds are more prized than others

 

[Tom Hill]

In an attempt of furthering the understanding, and help folks see through some of the breeder jargon and look at the family lines...

I used "Mexico" as P1, and "Afghanistan" as P2, for a reason. Both of the parents used to achieve the F1 must "breed true" for desired traits in order to yield a truly homogeneous (uniform) progeny. So, while many breeders would like to call the offspring of (A) x (B) an F1, it's very often a misnomer and the progeny is not homogeneous because a/the parent/s did not breed true for said traits.

At the risk of offending anyone (surely not my intention) I'll offer the following example using people color as our desired trait. White girl x white guy = white children - if that is always the case then the parents are said to breed true for that trait. White girl x black guy = the F1 mulatto (predictably - as the trait seems to be codominant). It is this predictability -among other things- that breeders attempt to exploit in the F1.

The F2 is where things really begin to get interesting though as genotypes are recombined. This is where we get beautiful blond afro babies with green eyes and mocha skin etc, more beautiful than any of the original parents. Some of these F2 individuals will be true breeding for these desired traits, and some won't. Genotype testing is required to discover which are which.

In the backcrossing example, if the "recurrent" parent (P1) that is used over and over does not breed true for the desired traits, then no amount of backcrossing will bring the resulting population -as a whole- any closer to them. -Tom

 

[Darwin]

To provide a graphical illustration of what Tom just said (please don't take offense to my elaborating) consider the following over-simplified example:

Lets assume that the desired trait of the P1 is a simple Mendelian trait: AA=desired expression.

AA (the P1) x even aa (the bc) will result in:
a a
A Aa Aa
A Aa Aa

Any of those offspring back-crossed to the parent would give:
A a
A AA Aa
A AA Aa

Proper selection (for the AA) would therefore result in a stabilized parent in the resulting generation.

Let's however assume that the desired trait in the parent Aa either through incomplete or codominance. In no permutation can that Aa phenotype be completely fixed. Of course if you breed an AA parent with an aa parent you will get the desired offspring but these will not be true-breeding for the trait.

In the real world, this gets even more complicated. In the skin color example Tom provided, there are actually several different alleles within several different genes coding for skin color. In this case the combination of any given phenotypes can result in a vast array of phenotypes in the resulting generation. Things get incredibly complicated.

I hope this helped the learning process

edit: sorry my punnet squares didn't come out right, I can't figure out how to get them aligned properly.

 

[the gnome]

so in the case of the sour bubble BX4 seeds,

I would expect there would be many, many more variations that I could expect to see before I expect to find the one that was identical or as near as possible had the original traits to the F1

is this a logical conclusion

 

[Tom Hill]

One would assume that if someone went through the trouble of making BC4 seed, that they would first go through the much less trouble of being certain that the recurrent parent was relatively homozygous (true breeding) for the valuable traits outlined in the goal. Of course you know what they say about assumptions. I tried to use the search function briefly to try to come up with an educated guess for you, only to come up with a blurry picture of what the genetics of Sour Bubble even are. The breeder would be able to answer these questions for you. -T

 

[Raco]

In an attempt of furthering the understanding, and help folks see through some of the breeder jargon and look at the family lines...

I used "Mexico" as P1, and "Afghanistan" as P2, for a reason. Both of the parents used to achieve the F1 must "breed true" for desired traits in order to yield a truly homogeneous (uniform) progeny. So, while many breeders would like to call the offspring of (A) x (B) an F1, it's very often a misnomer and the progeny is not homogeneous because a/the parent/s did not breed true for said traits.

At the risk of offending anyone (surely not my intention) I'll offer the following example using people color as our desired trait. White girl x white guy = white children - if that is always the case then the parents are said to breed true for that trait. White girl x black guy = the F1 mulatto (predictably - as the trait seems to be co-dominant). It is this predictability -among other things- that breeders attempt to exploit in the F1.

The F2 is where things really begin to get interesting though as genotypes are recombined. This is where we get beautiful blond afro babies with green eyes and mocha skin etc, more beautiful than any of the original parents. Some of these F2 individuals will be true breeding for these desired traits, and some won't. Genotype testing is required to discover which are which.

In the backcrossing example, if the "recurrent" parent (P1) that is used over and over does not breed true for the desired traits, then no amount of backcrossing will bring the resulting population -as a whole- any closer to them. -Tom

Muy buen post Señor easily understandable

 

[resin_lung]

crystal clear.

 

[the gnome]

thanks for explaning it in a way thats easy to comprehend tom!

 

[Azra'eil]

hello fellows , can i ask a question ? this not about backcrossing and this not something i plan to do, just something i don't understand.

We say we have two unrelated F1 lines (two heterozygous lines) and we want to cross them together. We will consider the aroma trait. To simplify we will say this is a monogenic trait. (a trait controlled by only one gene pair)
The mother we will use have a mango aroma and we know the father we will use have a pineapple aroma because we reversed a clone of him and produced a few female flowers to find it.
So the mango aroma is heterozygous dominant (Aa) in the mother and the pineapple aroma is heterozygous dominant (Aa) in the father.
we cross the two and the results show us that one plant will be homozygous dominant, one will be homozygous recessive and two plants will be heterozygous. But the two plants who are homozygous can't be homozygous because they have not the same version of the gene so what's happen ? im confused.....lol

A a
A AA Aa
a Aa aa