2006problemset8key

2006problemset8key - 1 Problem Set #8 KEY - BICD 100 W' 06...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
1 1 Problem Set #8 KEY - BICD 100 W’ 06 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 c. Based on your answers in part b, what floral phenotype would you expect in a double mutant that is homozygous for loss-of-function mutations in i. AP2 and AP3 ? In a double ap2; ap3 mutant, only AG remains. If AG is expressed in all whorls, then all organs will develop as carpels. You might have said that you can't predict what would happen to whorl 1 and 2 organs because none of the genes would be expressed there – if so, that's OK. But in reality, AP2 suppresses expression of AG in whorls 1 and 2, so in the absence of AP2 , AG is expressed in all whorls and all organs develop as carpels. ii.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/17/2008 for the course BICD 100 taught by Professor Nehring during the Winter '08 term at UCSD.

Page1 / 4

2006problemset8key - 1 Problem Set #8 KEY - BICD 100 W' 06...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online