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F1 crosses - First Filial Crosses |
The F1 or first filial cross was first described by Mendel
(1865). The F1 cross is generally given very little attention
in most genetics textbooks. These books seldom discuss its
analytical power, especially in relationship to sex-linked traits and the
different dominance relationships. All too often the F1
cross is treated as a "trivial" cross that
one does on the way to "more interesting crosses" such as the F2
(second filial cross) or the various backcrosses.
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Mendel's Original Paper (in translation)
http://www.esp.org/foundations/genetics/classical/gm-65.pdf Information Available from the F1 and F1
reciprocal progeny. The F1 cross is very important in its own right.
First, heterozygous F1 progeny illustrate Mendel's principle of
uniformity How
to Do an F1 and F1
reciprocal cross To do an
F1 cross you need two pure-breeding or homozygous
lines. Such homozygous lines are also called parental lines
Females from one of the parental lines (Parental Line
1 or P1) are mated to males from the other parental line (Parental Line
2 or P2). The mating is called the F1 cross and the progeny resulting from this mating are the
F1 progeny or
F1 generation.
Alternatively, P2 females can be mated with P1 males. from
Parental Line 1. This is called the reciprocal F1
cross (or the F1
reciprocal or F1R cross) and the progeny from this mating are the reciprocal F1 progeny
or the reciprocal F1 generation.
These crosses are illustrated below
Genetic analyses are done on the phenotypes of the
F1 progeny.
Classic Paper
.
Second, when they make gametes, the heterozygous F1 progeny illustrate Mendel's principle of
segregation
. Finally, by looking at the phenotypes of the F1 and F1
reciprocal progeny
you can determine:
(a)
whether the traits are dominant, incompletely
dominant, overdominant, codominant, or
recessive
and
(b)
whether the traits are autosomal or
sex-linked
.
Parental Lines differ in a pair of contrasting traits (e.g, red eyes or white
eyes in Drosophila, tall or short pea plants). 
Alternative Wording
The F1 cross is called the Parental cross
in some introductory genetic text books. The important distinction is to
separate the experimental mating (cross) from the resultant progeny or
generation. Whether you use the term F1 cross or the
term Parental cross the resulting progeny of that mating are the F1 progeny or the F1
generation.