Agriculture Reference
In-Depth Information
What he has done here is to mate 2 individuals that are heterozygous
(e.g., Ss) for a seed shape trait. In this group the resulting offspring
will be:
SS
Ss
ss
This means that:
25% of the offspring are homozygous for the dominant allele (BB).
50% are heterozygous like their parents (Bb) and
25% are homozygous for the recessive allele (bb).
Bingo! Remember this a few pages back?
In his first cross to create the hybrid plant Mendel ended up
with NO recessive traits for seed shape. But when he crossed the
offspring because they where heterozygous for that trait he ended up
with some having the recessive trait, some having the homozygous
trait and some continuing the heterozygous trait.
In correct breeding terms his first cross between the plants is
called the F1 cross or F1 generation. The breeding out of those
offspring is called the F2 cross or F2 generation.
Now since he has Ss, ss and SS to work with you can probably
do the Punnett square for each to see how they will work out. It would
be a good time to test your knowledge on this. Compare your results
with what you have learned about ratios in this chapter and you will be
able to see how it all fits together. It is really very simple once you
