CORN BREEDING 
13 
"would be red aleurone into purple aleurone. The factor pairs A a, 
C c, R ?\ and Pr pr are alike in that the dominant allelomorph of 
each is necessary for the development of the color. 
The fifth pair of factors concerned in aleurone color formation / i, 
differs from the others in that the dominant member inhibits color, 
regardless of the other four factor pairs. Thus, kernels containing 
either 1 1 or I i have colorless aleurone, although they may be A A, 
O C,RR,PrPr. 
The behavior of two of the factor pairs, A a and R r, in a cross 
between colorless strains of corn is shown in Figure 6. One of the 
parents is colorless because it is a a and the other because it is r r. 
All of the F x kernels of the cross will have red aleurone, the neces- 
sary A factor being brought in by one parent and the R factor by 
the other. Actually, if R is brought in by the male parent the result- 
ing kernels may be colored less deeply than if R comes in from the 
female parent, as a single dose (R) from the male is not completely 
dominant over a double dose (r r) from the polar nuclei. The dis- 
tinction between colored and colorless aleurone is clear, however, 
and for the sake of simplicity the extra set of chromosomes from 
the female parent is not indicated in Figure 6. As both of the 
parent strains are assumed to be homozygous i i, C C, pr pr, all of 
the reproductive cells formed by either strain will contain i, C ', pr, 
and all of the progeny will be like the parents for these factors. The 
pr factor is not shown in the figure. Its behavior is entirely similar 
to that of i or G . 
If the F x generation is self-fertilized the character of the aleurone 
in the second generation will depend upon the way in which the 
four types of reproductive cells shown in Figure 6 chance to come 
together during fertilization. There are 16 possible combinations, 
and if large numbers of kernels are classified each combination will 
be found to occur in approximately one-sixteenth of the total num- 
ber of kernels. Considering the kernels only as colored and color- 
less, it is immaterial whether a given factor comes in from the male 
or the female side, and on this basis the combinations may be 
grouped as shown in Table 1. 
Table 1. — Number of colored and colorless kernels in the F 2 generation of corn, 
resulting from the chance combinations of the four kinds of reproductive 
cells shown in Figure 6 
Kernels 
Group 
Factors present i 
Aleurone color 
Average 
number 
in 
every 
16 
a 
>i i, C C, pr pr 
{A A, R R ... 
Red 
1 
b 
A A, R t 
do 
2 
c 
A a, R R 
..do 
2 
d 
A a, Rr 
do 
4 
e 
A A, T r 
1 
f 
do 
2 
g 
a a, R R 
do - 
1 
h 
a a, R r 
. do. 
2 
i 
do 
1 
i Both parents were assumed to be homozygous for the factors indicated by the braces, and these there- 
fore are carried by all of the kernels. 
