Flower Mutation, ABCDE Model of Flower Development

Here is a detailed set of 25 medium to advanced-level MCQs related to floral mutations and floral organ identity genes, aligned with the your CSIR Life Science examination pattern:  

1. Which of the following gene classes is responsible for determining the identity of sepals in Arabidopsis?

A) Class A  

B) Class B  

C) Class C  

D) Class E  

Ans - A  

2. A mutation in the AGAMOUS (AG) gene leads to:

A) Conversion of sepals to petals  

B) Conversion of reproductive organs into perianth organs  

C) Development of extra carpels  

D) Loss of floral meristem determinacy  

Ans - B  

3. Which genes form the core of the ABC model of flower development?

A) Apetala1, Apetala3, Agamous  

B) Sepallata, Pistillata, Apetala3  

C) Apetala1, Agamous, Sepallata  

D) Pistillata, Agamous, Apetala1  

Ans - A  

4. The APETALA1 (AP1) gene is involved in:

A) Sepal and petal identity specification  

B) Petal and stamen identity specification  

C) Stamen and carpel identity specification  

D) Floral meristem determinacy  

Ans - A  

5. Which gene, when mutated, leads to the transformation of petals into sepals?

A) Pistillata (PI)  

B) Apetala3 (AP3)  

C) Apetala1 (AP1)  

D) Sepallata (SEP)  

Ans - B  

6. Class C genes in the ABC model are required for the development of:

A) Sepals and petals  

B) Petals and stamens  

C) Stamens and carpels  

D) Sepals and carpels  

Ans - C  

7. What is the phenotype of the apetala3 (ap3) mutant?

A) Sepals in the first and second whorls  

B) Petals in the second and third whorls  

C) Sepals in the first whorl and petals in the second  

D) Sepals in the second whorl and carpels in the third  

Ans - A  

8. What is the role of the SEPALLATA (SEP) genes?

A) They repress Class C gene expression.  

B) They act as cofactors for Class A, B, and C genes.  

C) They specify sepal identity.  

D) They control the determinacy of the floral meristem.  

Ans - B  

9. In a pistillata (pi) mutant, what floral organ identity is observed in the second and third whorls?

A) Sepals and carpels  

B) Petals and stamens  

C) Sepals and stamens  

D) Petals and carpels  

Ans - A  

10. Which genes are responsible for specifying petal identity in Arabidopsis?

A) Class A and Class B genes  

B) Class A and Class C genes  

C) Class B and Class C genes  

D) Class A and Class E genes  

Ans - A  

11. Which of the following is NOT true about the ABC model of floral development?

A) Class A genes are expressed in the first and second whorls.  

B) Class C genes repress Class A genes in the third and fourth whorls.  

C) Class B genes are expressed only in the second and third whorls.  

D) Class B genes repress Class C genes in the fourth whorl.  

Ans - D  

12. The term "homeotic transformation" in the context of floral mutations refers to:

A) Loss of floral organs  

B) Replacement of one organ type by another  

C) Overproduction of floral organs  

D) Complete sterility of the flower  

Ans - B  

13. A plant with repeated "sepal-petal-petal" structures is most likely a mutant of:

A) AP1  

B) AP3  

C) AG  

D) PI  

Ans - C  

14. What happens if both Class A and Class C gene functions are lost?

A) The flower becomes a leaf-like structure.  

B) The flower produces only petals.  

C) The flower becomes indeterminate with sepals and petals repeated.  

D) The flower produces only stamens.  

Ans - C  

15. Which genes specifically determine stamen identity in Arabidopsis?

A) AP1 and AP3  

B) AP3 and PI  

C) PI and AG  

D) AP1 and AG  

Ans - B  

16. The LEAFY (LFY) gene in Arabidopsis is involved in:

A) Stamen identity  

B) Carpel identity  

C) Floral meristem initiation  

D) Repressing vegetative growth  

Ans - C  

17. The AGAMOUS gene product functions as a:

A) Repressor of Class B genes  

B) Activator of floral meristem genes  

C) Transcription factor  

D) Hormone transporter  

Ans - C  

18. In the ABCDE model of flower development, the "E" class genes are essential for:

A) Sepal formation  

B) Petal formation  

C) Floral organ identity specification  

D) Floral meristem maintenance  

Ans - C  

19. In the quadruple sepallata (sep1/2/3/4) mutant, the flowers resemble:

A) Leaf-like structures  

B) Only sepals  

C) Petals and stamens  

D) Carpels and stamens  

Ans - A  

20. Loss-of-function mutations in which gene lead to indeterminate floral meristems?

A) AG  

B) PI  

C) SEP  

D) AP1  

Ans - A  

21. Which of the following is true for the B-class mutants (ap3 or pi)?

A) Petals are converted to sepals.  

B) Stamens are converted to sepals.  

C) Both A and B.  

D) Petals are converted to carpels.  

Ans - C  

22. Class D genes in the extended ABCDE model are specifically involved in:

A) Petal formation  

B) Ovule development  

C) Floral meristem initiation  

D) Sepal formation  

Ans - B  

23. A double mutant of AP1 and LFY will result in:

A) Indeterminate flowers  

B) Complete loss of floral identity  

C) Replacement of petals with sepal

D) Overproduction of stamens  

Ans - B  

24. Which protein complex is critical for the activation of floral organ identity genes?

A) SEP-AP1 complex  

B) AP1-LFY complex  

C) SEP-AP3-PI complex  

D) PI-AG complex  

Ans - C  

25. The phenotype of a triple mutant for SEP genes in Arabidopsis is:

A) Indeterminate floral meristems with repeated floral organs  

B) Complete transformation of floral organs into vegetative structures  

C) Loss of stamen and carpel identity only  

D) Overproduction of petals  

Ans - B  

Roles of floral homeotic genes, mutations, and their effects, following the ABC and ABCDE models of flower development, with a focus on Arabidopsis thaliana.

25 comprehensive MCQs covering basic to advanced aspects of the ABCD model of flower development, designed to enhance your understanding for CSIR NET Life Sciences.  

1. Which whorls are specified by Class A genes in the ABC model?

A) Sepals and petals  

B) Petals and stamens  

C) Stamens and carpels  

D) Sepals and carpels  

Ans:A  

2. In the ABCD model, Class D genes specifically control:

A) Floral meristem initiation  

B) Petal development  

C) Ovule development  

D) Sepal identity  

Ans - C  

3. Loss of function in both Class B and Class C genes leads to the formation of:

A) Sepals only  

B) Sepals and petals only  

C) Stamens and carpels only  

D) Indeterminate flowers  

Ans - B  

4. Which two genes are classified as Class B in the ABC model?

A) AP1 and PI  

B) PI and AP3  

C) AP3 and AG  

D) PI and AG  

Ans - B  

5. The expression of Class C genes in Arabidopsis is restricted to which whorls?

A) First and second  

B) Second and third  

C) Third and fourth  

D) First and fourth  

Ans -C  

6. What is the outcome of a mutation in both Class A and Class B genes?

A) Stamens and carpels form in all whorls.  

B) Sepals and petals form in all whorls.  

C) Carpels form in the first and fourth whorls, stamens in the second and third.  

D) The flower becomes indeterminate.  

Ans - A  

7. The ABCD model of floral development was first elucidated in:

A) Petunia  

B) Arabidopsis and Antirrhinum  

C) Rice  

D) Brassica  

Ans - B  

8. Class A gene expression is repressed by which class of genes?

A) Class B  

B) Class C  

C) Class D  

D) Class E  

Ans - B  

9. What is the phenotype of a Class C mutant flower?

A) Sepals in the first and second whorls, petals in the third and fourth whorls  

B) Sepals in all four whorls  

C) Petals in the first and second whorls, stamens in the third and fourth whorls  

D) Stamens and carpels in all whorls  

Ans - A  

10. Which of the following floral organs arise from the third whorl in wild-type Arabidopsis flowers?

A) Sepals  

B) Petals  

C) Stamens  

D) Carpels  

Ans - C  

11. The combinatorial expression of which gene classes is required for stamen identity?

A) A + B  

B) B + C  

C) B + D  

D) A + C  

Ans - B  

12. The role of Class E (SEPALLATA) genes in the ABCDE model is to:

A) Determine carpel identity only.  

B) Act as cofactors for all other classes.  

C) Repress Class D gene expression.  

D) Specify sepal identity.  

Ans - B  

13. Which of the following is true about ovule development?

A) Controlled by Class C and D genes  

B) Controlled by Class D genes only  

C) Controlled by Class B and C genes  

D) Controlled by all ABCD classes  

Ans - A  

14. In the ABC model, the identity of petals is determined by:

A) A + C gene expression  

B) A + B gene expression  

C) B + E gene expression  

D) B + D gene expression  

Ans - B  

15. What happens in a quadruple mutant of SEP genes (sep1/2/3/4)?

A) Floral organs convert to vegetative structures.  

B) Carpels form in all whorls.  

C) Sepals and petals form repeatedly.  

D) The flower becomes completely sterile.  

Ans - A  

16. In the absence of Class B gene function, the floral organs in the second and third whorls are replaced by:

A) Sepals and petals  

B) Sepals only  

C) Carpels and stamens  

D) Sepals and carpels  

Ans - D  

17. Which experimental method is commonly used to study gene expression patterns in the ABC model?

A) Southern blotting  

B) In situ hybridization  

C) Protein sequencing  

D) Chromatography  

Ans - B  

18. Overexpression of the AGAMOUS gene leads to:

A) Complete conversion of flowers to leaves.  

B) Loss of sepal and petal identity.  

C) Overproduction of stamens and carpels.  

D) Loss of floral meristem activity.  

Ans - C  

19. Which of the following is NOT a component of the floral quartet model?

A) AP3  

B) SEP  

C) PI  

D) LFY  

Ans - D  

20. The organ identity of carpels in Arabidopsis is determined by:

A) Class C genes alone  

B) Class C and D genes  

C) Class C and E genes  

D) Class B and C genes  

Ans - C  

21. Which statement about the ABC model is correct?

A) Class A and Class C genes are mutually repressive.  

B) Class B genes are expressed in all four whorls.  

C) Class D genes are involved in floral meristem identity.  

D) Class E genes act independently of the ABC classes.  

Ans - A  

22. A triple mutant for Class B genes (AP3/PI) would result in:

A) Flowers with only stamens and carpels.  

B) Flowers with sepals in the first and second whorls, carpels in the third and fourth.  

C) Indeterminate floral meristems.  

D) Flowers with only petals and carpels.  

Ans - B  

23. The SEP genes belong to which family of transcription factors?

A) MADS-box  

B) Helix-turn-helix  

C) Leucine zipper  

D) Homeodomain  

Ans - A  

24. The "floral quartet" refers to a complex of proteins required for:

A) Petal and stamen formation  

B) Floral organ identity determination  

C) Floral meristem initiation  

D) Ovule and carpel development  

Ans - B  

25. The role of floral homeotic genes is primarily to:

A) Regulate photosynthesis.  

B) Control floral organ identity.  

C) Determine vegetative organ development.  

D) Regulate seed germination.  

Ans - B  

These 25 MCQS are designed to gradually build your understanding of the ABCDE model, from basics to more intricate interactions and phenotypic outcomes.

These questions comprehensively cover the basics, advanced concepts, and experimental aspects of the ABCD model of flower development, ensuring thorough preparation for your Life Sciences exam.

Basic Questions:

1. What does the "A" in the ABCDE model primarily regulate?

   a) Sepals and petals  

   b) Petals and stamens  

   c) Carpels and ovules  

   d) Stamens and carpels  

Ans - A

2. Which gene class is required for stamen formation?

   a) A  

   b) B  

   c) C  

   d) D  

   

Ans - B

3. What phenotype is observed when the "C" gene function is lost?

   a) No sepals form  

   b) All floral organs become sepals and petals  

   c) No petals form  

   d) Stamens are replaced by sepals  

Ans - B

4. Which of the following are B-class genes? 

   a) APETALA1 and APETALA2  

   b) APETALA3 and PISTILLATA  

   c) AGAMOUS and SEPALLATA  

   d) SHATTERPROOF1 and SHATTERPROOF2  

   

Ans - B

5. The "E" class genes are required for the formation of which floral organs?

   a) Sepals  

   b) Petals  

   c) All floral organs  

   d) Ovules only  

   

Ans - C

6. Which genes form the A-class group in Arabidopsis thaliana?

   a) AGAMOUS and SEPALLATA  

   b) APETALA1 and APETALA2  

   c) APETALA3 and PISTILLATA  

   d) SHATTERPROOF1 and SHATTERPROOF2  

Ans - B

7. What happens in a "B-class" mutant? 

   a) Sepals replace petals; carpels replace stamens  

   b) Stamens replace petals; sepals remain normal  

   c) Carpels replace sepals; petals remain normal  

   d) All floral organs are replaced by carpels  

   

Ans - A

8. What does the "C" gene control in flowers?

   a) Sepal identity  

   b) Petal identity  

   c) Stamen and carpel identity  

   d) Ovule development only  

   Ans - C

9. What type of protein are ABCDE genes?

   a) Transport proteins  

   b) Transcription factors  

   c) Enzymes  

   d) Hormones  

   

Ans - B

10. What does the combination of A+B genes specify?

    a) Sepal identity  

    b) Petal identity  

    c) Stamen identity  

    d) Carpel identity  

    

Ans - B

Intermediate Questions

11. What is the primary role of the D-class genes?  

    a) Formation of petals  

    b) Ovule development  

    c) Sepal identity  

    d) Regulation of ABC genes  

    

Ans - B 

12. Which genes interact with E-class genes for organ development?

    a) Only A-class genes  

    b) Only B-class genes  

    c) All A, B, C, and D-class genes  

    d) None of the above  

    

Ans - C

13. What happens if both A and C genes are inactivated?

    a) Only sepals form  

    b) Only petals form  

    c) No floral organs form  

    d) Leaf-like structures replace all floral organs  

    

Ans - D

14. What is the phenotype of a triple mutant lacking all E-class genes? 

    a) Only sepals develop  

    b) Only petals develop  

    c) No floral organs form  

    d) Stamens are converted to sepals  

    

Ans - C

15. Which of the following is NOT an A-class gene?

    a) APETALA1  

    b) APETALA2  

    c) AGAMOUS  

    d) None of the above  

    

Ans - C

16. What is the significance of SEPALLATA genes?

    a) They specify only ovule development  

    b) They act as cofactors for ABCD gene functions  

    c) They are redundant and not required for flower formation  

    d) They repress A-class genes  

    

Ans - B 

17. What does the combination of B+C genes specify?

    a) Sepals  

    b) Petals  

    c) Stamens  

    d) Carpels  

    

Ans - C

18. Which mutant leads to the "carpelloid" phenotype in sepals and petals?

    a) Loss of B genes  

    b) Loss of C genes  

    c) Loss of D genes  

    d) Overexpression of AGAMOUS  

    

Ans - B  

19. The ABCDE model is an extension of which previous model?

    a) Homeotic model  

    b) ABC model  

    c) Gene activation model  

    d) Floral quartet model  

    

Ans - B

20. What is the floral quartet model's basis?

    a) Genes directly activate each organ  

    b) Protein complexes of ABCDE genes specify organ identity  

    c) Hormonal gradients determine organ identity  

    d) All organs are predetermined genetically  

   

Ans - B

Advanced Questions

21. Which of the following genes belong to the D-class in Arabidopsis? 

    a) APETALA3 and PISTILLATA  

    b) SHATTERPROOF1 and SHATTERPROOF2  

    c) SEPALLATA1 and SEPALLATA2  

    d) APETALA1 and APETALA2  

    

Ans - B 

22. What phenotype is observed in an AGAMOUS overexpression mutant? 

    a) Sepals and petals are converted to carpels  

    b) Petals and stamens are converted to sepals  

    c) Ovules fail to develop  

    d) No significant changes  

Ans - B

23. Which of the following is true for APETALA3-PISTILLATA heterodimers? 

    a) They regulate D-class genes  

    b) They specify stamen and petal identity  

    c) They repress A-class genes  

    d) They induce SEPALLATA expression  

    

Ans - B

24. What happens in a C-class mutant where AGAMOUS is non-functional?

    a) Sepals and petals replace stamens and carpels  

    b) Stamens replace sepals  

    c) Carpels replace petals  

    d) Ovules are hyperdeveloped  

    

Ans - A  

25. The interaction of ABCDE genes with E-class genes forms what kind of structure?

    a) Protein tetramers binding to DNA  

    b) Homodimers acting on RNA  

    c) Signal transduction cascades  

    d) Microtubules for organogenesis  

    

Ans - A