Qualitative and Quantifiable Mendel
032906PHW
A genetics activity with rapid cycling Brassica rapa
Graphs of the patterns of inheritance in
the F1 and F2 generations resulting from
the cross of mothers (P1) having the qualitatively expressed gene, anthocyaninless
(anl=pure green plants) with purple males
(P2). Also represented in the cross is
the quantifiable phenotype petite dwarf
(dwf1), expressed as reduced size of
plant parts. In the graphs of the cross
depicted, the width of the largest cotyledon (mm) is measured on plants at 7 days
after sowing.
Frequency histograms of 7 day old cotyledon widths of parental (P1, P2), F1, & F2
populations graphed in various combinations
to illustrate patterns of segregation of the
qualitatively described trait (color) and
the quantifiable, intermediately expressed
trait, cotyledon size (mm).
P2
P1
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Cotyledon width,mm, 7days old
P1=maternal parents,
n=12, stock,C1-107,
anl,Hir(1),mst2/1:1.
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Cotyledon width,mm, 7days old
P2=paternal parents
n=12,stock,C1-77,
dwf1,Pan(8),Hir(5)
P2
F1
P1
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Cotyledon width,mm, 7days old
P1,P2,F1,
F2
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Cotyledon width,mm, 7days old
F1 generation,
n=12,stock,C1-139
anl/+,+/dwf1,
Hir(1/5)
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Cotyledon width,mm, 7days old
F2 generation,
n=36,stock,C1-140,
segregating for,
anl, dwf1 & Hir
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Cotyledon width,mm, 7days old
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Cotyledon width,mm, 7days old
The parental stocks used in this activity also exhibit contrasting expression of the quantitatively
inherited trait, hairs (Hir). P1 stock C1-107 as well
as being anthocyaninless (anl =green) and male sterile (mst2/1:1), is hairless (Hir(1)). The P2 stock
C1-77, is petite dwarf (dwf1), strongly purple,
Pan(8), and moderately hairy (Hir(5)). Intensity
of Pan expression is also quantitatively inherited
and strongly influenced by environment. High light
intenisty ,low nutrients and cool temperatures enhance Pan expression. Expression of hairs is relatively stable under various enviromnents. Detailed
information on genetic decriptions of these and
other stocks is at,www.fastplants.org under Rapid
Cycling Brassica Collection.