2008problemset9key

2008problemset9key - ProblemSet#9KEY BICD100W08 1

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Problem Set #9 KEY BICD 100 W’ 08 1.) Many plants produce flowers consisting of four organ types arranged in concentric "whorls". In wild-type Arabidopsis thaliana , whorl 1 organs are sepals (green leaf-like organs that protect the flower before it has opened), whorl 2 organs are petals, whorl 3 organs are stamens (male reproductive structures that make pollen), and whorl 4 organs are carpels (female reproductive structures containing eggs). Geneticists have isolated homeotic mutations that define several genes required for proper specification of floral organ identities. The following illustrations show the phenotypes of plants homozygous for loss- of-function mutations in the genes AGAMOUS ( AG ), APETALA2 ( AP2 ) and APETALA3 ( AP3 ) (see original problem set for illustrations). a. What can you conclude from these mutant phenotypes about the function of each of the following genes (next page)? Be as specific as possible. i. AGAMOUS: This gene is required to specify the identities of 3 rd and 4 th whorl organs as stamens and carpels, respectively ii. APETALA2: This gene is required to specify the identities of 1 st and 2 nd whorl organs as sepals and petals, respectively. iii. APETALA3: This gene is required to specify the identities of 2 nd and 3 rd whorl organs as petals and stamens, respectively b. Which of the following models for the functions of the wild-type genes is consistent with the data provided? (Circle each answer that is consistent with the data) >i. co-expression of AG and AP3 genes causes a floral organ to develop as a stamen ii. co-expression of AG and AP3 genes causes a floral organ to develop as sepal iii. co-expression of AP3 and AP2 genes causes a floral organ to develop as a carpel >iv. co-expression of AP3 and AP2 genes causes a floral organ to develop as a petal v. expression of AP2 alone causes an organ to develop as a carpel or a stamen >vi. expression of AP2 alone causes an organ to develop as a sepal >vii. expression of AG alone causes an organ to develop as a carpel viii. expression of AG alone causes an organ to develop as a sepal or a petal
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This note was uploaded on 11/14/2008 for the course BICD 100 taught by Professor Nehring during the Spring '08 term at UCSD.

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2008problemset9key - ProblemSet#9KEY BICD100W08 1

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