lec 30- flower production

Question 1

what are the 4 types of reproductive organs seen arranged radically symmetrically in arabidopsis? what is their purpose?

Answer 1

Carpels- contain the ovules that produce seeds after fertilization
Stamens- produce pollen grains (male gametes)
Petals- attract pollinators
Sepals- enclose the flower bud before it opens

Question 2

what model explains how floral meristem produces flowers?

Answer 2

ABC model

Question 3

explain the ABC model:

Answer 3

organ identities are specified by combinations of transcription factor activites

-sepals are produced from just the A gene
-petals are produced from A and B genes
-stamens are produced from C and B genes
-carpels are produced from just the C gene

Question 4

what 1st mutant supports the ABC model?

Answer 4

-mutant plants carrying mutations in AP1 and AP2 genes produce whorls of carpels and stamens
-they are missing the A gene activity
-becaus ethe carpel and stamen are produced throughout the flower, it means that A and C repress one another, once one is missing, the remaining one can take over the missing ones spot

Question 5

what is the second mutant that supports the ABC model?

Answer 5

-mutant plants carrying mutations in AP3 and P1 genes produce whorls of sepals and carpels
-they are missing B gene activity

Question 6

what is the third mutant that supports the ABC model?

Answer 6

-mutant plant carrying mutations in the AG gene producing whirls of sepals and petals
-they are missing C gene activity
-A becomes active across the flower

Question 7

what happens if all three transcription factor activities are missing? are the ABC genes necessary?

Answer 7

-the mutant develops flowers in which the organs are replaced by green leaf-like structures
-it is a flower as it is produced by floral meristem
-this tells us that ABC genes are necessary for floral organ development

Question 8

what happens if ABC genes are expressed throughout the plant?

Answer 8

-leaves are not transformed into floral organs, meaning something other then the ABC genes are needed to make floral organs
-this means ABC genes are not sufficient

Question 9

what are the other genes needed along the ABC genes to produce floral organs?

Answer 9

SEP1, SEP2, and SEP3

Question 10

are the genes that determine floral organ identities homeotic genes?

Answer 10

yes, they can also cause homeotic mutations

Question 11

what encodes the DNA binding region in the genes that determine organ identity?

Answer 11

MADS boxes

Question 12

is ABC modified in other plants?

Answer 12

yes, to produce different amounts of each organ