Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

33. Plant Anatomy

Growth

General Biology

33. Plant Anatomy

Growth

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0:48 minutes

Problem 5

Textbook Question

Suppose a flower had normal expression of genes A and C and expression of gene B in all four whorls. Based on the ABC hypothesis, what would be the structure of that flower, starting at the outermost whorl?
a. Carpel-petal-petal-carpel
b. Petal-petal-stamen-stamen
c. Sepal-carpel-carpel-sepal
d. Sepal-sepal-carpel-carpel

Verified step by step guidance

Understand the ABC model of flower development: The ABC model explains how the identity of floral organs is determined by the expression of three classes of genes: A, B, and C. Each gene class is responsible for the development of specific whorls in the flower.

Identify the role of each gene class: Gene A is responsible for sepals, Gene B for petals and stamens, and Gene C for stamens and carpels. The combination of these genes determines the identity of the floral organs in each whorl.

Analyze the given gene expression: The problem states normal expression of genes A and C, and expression of gene B in all four whorls. This means gene A is expressed in the first whorl, gene B in all whorls, and gene C in the third and fourth whorls.

Determine the structure of each whorl: Based on the ABC model, the first whorl with gene A expression will form sepals. The second whorl with gene A and B expression will form petals. The third whorl with gene B and C expression will form stamens. The fourth whorl with gene C expression will form carpels.

Match the structure to the options: The sequence of floral organs from outermost to innermost whorl is sepal-petal-stamen-carpel. Compare this sequence with the given options to identify the correct answer.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

ABC Model of Flower Development

The ABC model explains how the identity of floral organs is determined by the expression of three classes of genes: A, B, and C. Class A genes specify sepals, A and B together specify petals, B and C specify stamens, and C alone specifies carpels. This model helps predict the arrangement of floral organs based on gene expression patterns.

Gene Expression in Floral Whorls

Floral organs are arranged in concentric whorls, typically four: sepals, petals, stamens, and carpels. The expression of specific genes in these whorls determines the type of organ formed. In the ABC model, the presence or absence of gene expression in each whorl dictates the organ identity, crucial for understanding flower structure.

Mutations and Gene Expression Patterns

Mutations affecting gene expression can alter the normal pattern of floral organ development. In the given scenario, the expression of gene B in all whorls suggests a mutation or alteration from typical expression patterns, leading to a change in organ identity. Understanding these patterns is essential for predicting the resulting flower structure.