Gregor Mendel 1822-1884
(ursprung Johann)
-abott i Brunn, Österrike,
Nuv Brno Tjeckien
-studerade fysik, matematik
och kemi i Vienna
-publ 1865, ”Versuche uber
Pflanzenhybriden”
-Darwin publ 1859 ”The
Origin of Spieces
Sid 60
Sid 61
Allele for purple flowers
Homologous
pair of
chromosomes
Locus for flower-color gene
Allele for white flowers
•
Sid 62
TECHNIQUE
×
Dominant phenotype, Recessive phenotype,
known genotype:
unknown genotype:
pp
PP or Pp?
Predictions
If PP
Sperm
p
p
P
P
Pp
Eggs
If Pp
Sperm
p
p
or
Pp
P
Eggs
Pp
Pp
pp
pp
p
Pp
Pp
1
–
EXPERIMENT
Sid 65
YYRR
P Generation
yyrr
×
Gametes YR
F1 Generation
Hypothesis of
dependent
assortment
Predictions
Hypothesis of
independent
assortment
Sperm
or
Predicted
offspring of
F2 generation
1/
2
yr
YyRr
1/
2
1/
4
Sperm
YR 1/2 yr
1/
4
YR
1/
4
Yr
YR
1/
4
1/
4
Yr
1/
4
yR
yr
YYRR
YYRr
YyRR
YyRr
YYRr
YYrr
YyRr
Yyrr
YyRR
YyRr
yyRR
yyRr
YyRr
Yyrr
yyRr
YR
YyRr
YYRR
Eggs
1/
2
Eggs
yr
YyRr
3/
4
yyrr
1/
4
yR
1/
4
Phenotypic ratio 3:1
1/
4
yr
3/
16
9/
16
3/
16
yyrr
1/
16
Phenotypic ratio 9:3:3:1
RESULTS
315
108
101
Phenotypic ratio approximately 9:3:3:1
32
•
sid 66
Sid 69
XNXN
Sperm Xn
N
Eggs X
XN
(a)
N n
X X
×
XnY
XNXn
Sperm XN
Y
N
X Y
×
N
Eggs X
XNXn XNY
Xn
(b)
N N
X X
XNY
XNXn
Sperm Xn
Y
N
X Y
N
Eggs X
XnXN XnY
Xn
N n
X X
×
XnY
Y
N
X Y
XnXn XnY
(c)
2
Sid 70
X chromosomes
Early embryo:
Two cell
populations
in adult cat:
Active X
Allele for
orange fur
Allele for
black fur
Cell division and
X chromosome
inactivation
Active X
Inactive X
Black fur
Orange fur
3