2. Flower Meristem Identity
Flowering Time FT
Flower Meristem Identity
APETALA1, LEAFY, CAULIFLOWER,
(TERMINAL FLOWER)
Flower Organ Identity
A, B, C
Fruit Development
FRUITFULL, SHATTERPROOF
INDEHISCENT

4. Goethe believed that floral organs are derived from leaves

5. sepal
petal
stamen
carpel B B A C C A 1 2 3 4 3 2 1

6. normal flower

7. What gene prevents the B gene from being
active in the center of flowers?
sepal
petal
stamen
carpel B A C

8. In SUPERMAN mutants (SUP), the B activity
expands into the center of the flower and converts
the two carpels into two stamens. B A C C A
stamen
sepal
petal

9. Superman mutant

10. The SUPERMAN gene normally functions to
prevent B gene activity in the center of flowers B A C C A
stamen
sepal
petal

11. normal
BC mutant ?? B B A C C A
sepal
petal
stamen
carpel A A A A

12. normal BC mutant sepal petal stamen carpel sepal sepal sepal sepal*

13. BC double
mutant
all organs
are sepals

14. What happens if the A, B and C genes are all
inactivated in the ABC triple mutant?
sepal
petal
stamen
carpel B A C

15. normal ABC mutant ?? sepal petal petal sepal carpel stamen stamen B A

16. normal ABC mutant sepal petal stamen carpel leaf leaf leaf * leaf leaf

17. “ABC” triple
mutant
all organs
are leaves

18. Goethe believed that floral organs are derived from leaves

19. The C gene is active in cells that will form stamens and carpels
petal
stamen
sepal
carpel
sepal
leaf
The C gene is active in cells that
will form stamens and carpels

20. petal stamen sepal carpel sepal leaf
What would happen if the C gene was mis-expressed
in cells that would normally form sepals?

21. add sepal on/off switch:
C GENE
CODING REGION
ON/OFF
stamens and carpels
remove on/off switch:
sepals
add sepal on/off switch:

22. normal B B A C C A
sepal
petal
petal
sepal
carpel
stamen
stamen

25. Ectopic B activity sepal petal petal sepal stamen stamen stamen B A C

27. Ectopic B activity A C B
petal
petal
petal
petal
stamen
stamen
stamen

28. Ectopic B
activity

29. Ectopic B and C activity
stamen
stamen
stamen
stamen
stamen
stamen
stamen

30. Ectopic B and C activity

31. Ectopic A and B activity
in C mutant B A
petal *

32. Ectopic A and B activity in a C mutant