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Question 1

In a comparison of plant and animal development, it is found that:

a) animals evolved from plants, and animal developmental strategies are derived from those of plants.

b) fully differentiated cells of plants are still totipotent, and will readily form a complete fertile plant, whereas the differentiated state of animal cells is difficult to reverse.

c) gene regulation evolved later than the split between plants and animals, and is executed differently in the two kingdoms.

d) basic metabolic pathways and intracellular structures evolved separately in plants and animals and are fundamentally different.

e) the developmental strategies of both plants and animals rely heavily on the migration of cells, such as occurs during gastrulation.

Question 2

Why has the diploid genome been an advantage in studying the development of Arabidopsis?

a) It is assumed that polyploidy plants use developmental mechanisms that are unlike those of animals, whereas the developmental mechanisms used by Arabidopsis are identical to those of animals, since both are diploid.

b) The diploid genome of Arabidopsis provides a marker for the Arabidopsis cells in chimeras made with other plants.

c) The diploid genome allows genetic analysis of development, in a manner analogous to the genetic analysis that has been done with Drosophila.

d) The development of polyploid plants is too variable to be of any use in studies of development.

e) Tetraploid plants develop twice as fast as diploid plants, hexaploid plants three times as fast and so on, making the study of development more difficult in polyploid pants.

Question 3

The fate map of the Arabidopsis embryo at the heart stage indicates that:

a) the primordia of the leaves, stems, and roots have already formed.

b) the three germ layers that will give rise to roots, stems, and leaves have formed.

c) a fate map the regions that will give rise to laves, stems, and roots can be drawn, although the cells are still undifferentiated, as is the case with the animal blastula.

d) although none of the adult structures have formed, the regions that will give rise to the meristems, which will in turn give rise to adult structures, can be identified.

e) development in plants is so indeterminate that a true fate map cannot be drawn.

Question 4

One of the earliest events in Arabidopsis development is formation of the _____ axis, in response to a gradient of _____.

a) apical-basal, auxin

b) dorsal-ventral, miRNA

c) apical-basal, Pin-1 and Pin-7

d) adaxial-abaxial, cytokinins

e) animal-vegetal, nodal

Question 5

The genetic analysis of Arabidopsis development was strongly influenced by genetic analysis of Drosophila development, and as is the case in Drosophila, genes that influence development are often named for:

a) extinct royal families of Europe.

b) mythical creatures from Greek mythology.

c) an alphabetical and numerical code such as B4 or H12, that indicates which well in a microtiter plate the mutant was found.

d) their location on a chromosome, as determined by karyotype analysis.

e) the phenotype observed when the gene is mutated.

Question 6

Maintenance of the shoot meristems in adult Arabidopsis plants relies on which of the following mechanisms?

a) A transcription factor encoded by the SHOOT MERISTEMLESS gene is expressed in shoot meristem cells and maintains them in their undifferentiated state.

b) A homeobox transcription factor encoded by the WUSCHEL gene is expressed in the organizing center and initiates a signal to the overlying cells to behave as stem cells.

c) Shoot meristems cells secrete proteins encoded by the CLAVATA family that antagonize WUSCHEL expression, thereby restricting the size of the shoot meristems.

d) All of the above are involved in specification and maintenance of shoot meristems.

e) Currently, nothing is known about the mechanisms that are involved in meristems behavior.

Question 7

Refer to Figure 6.18 on page 241 in the text: in the lower portion of the figure, where would leaf primordium number 7 appear?

a) Directly on the proximal (toward the center) side of leaf primordium number 6.

b) Directly opposite leaf primordium number 6, at the proximal junction of leaf primordia number 4 and number 5.

c) Directly opposite leaf primordium number 6, on the distal (toward the outside) side of the junction of leaf primordia number 1 and number 2.

d) Adjacent to leaf primordium number 6, on the proximal side of primordium number 4.

e) On the opposite, distal, side of leaf primordium number 3, relative to leaf primordium number 6.

Question 8

Which of the following describes the pathway in Arabidopsis by which day-length is translated into a signal that coverts a vegetative shoot meristem into a floral meristem?

a) The CONSTANS (CO) protein is degraded in the dark, but accumulates in the leaves as the days get longer.

b) The CONSTANS protein is a transcription factor, which turns on expression of the FLOWERING LOCUS T (FT) gene.

c) The FT mRNA travels to the shoot meristem, where it is translated; the protein then participates in activation of LEAFY and AP1.

d) LEAFY and AP1 re-specify the shoot meristem into a floral meristem, capable of producing flowers.

e) a through d above describe, in order, the pathway by which shoot meristems are turned into floral meristems.

Question 9

What is meant by the word 'whorl' in discussing floral meristems?

a) When leaf primordia first arise, they arise in a pattern described as a 'whorl'.

b) Flowers consist of four different types of organs, which occur in concentric rings called 'whorls'.

c) The floral meristem as to spin around during flower formation, giving the process the name 'whorl'.

d) The six stamens in a dicot flower like that of Arabidopsis form a ring that is called the flower's 'whorl'.

e) The flowers of Arabidopsis appear as the stem elongates in a pattern called a 'whorl'.

Question 10

In what way are the homeotic genes of flowering plants similar to those of Drosophila and other animals?

a) All homeotic genes are transcription factors of the homeobox class.

b) The homeotic genes of flowers are derived during evolution from the same primordial genes used in animals.

c) Mutations in the homeotic genes of flowers cause transformation of one organ into another.

d) The homeotic genes of plants are arranged in a cluster on the chromosome, and are expressed from one end to the other in an anterior-posterior order.

e) Homeotic genes in both plants and animals are transcription factors of the MADS-box type.

Question 11

What is the phenotype of a mutation in the AGAMOUS homeotic gene of Arabidopsis? (Recall, genes are often named for the mutant phenotype.)

a) AGAMOUS mutants fail to restrict the expression of class A genes, resulting in four whorls composed of sepals and petals, with no stamens or carpels.

b) AGAMOUS mutants fail to make the central-most whorl, which gives rise to carpels, and are thus left with only three whorls.

c) AGAMOUS mutants make only the outer two whorls, resulting in two whorls composed of sepals and petals, with no stamens or carpels.

d) AGAMOUS mutants make only the gamete-forming structures, stamens and carpels, with no petals or sepals.

e) AGAMOUS mutants have no phenotype in the absence of further mutations in the APETALA and PISTILLATA, since AGAMOUS is redundant to APETALA and PISTILLATA, and they substitute for it in its absence.

Question 12

How is the ABC model for floral identity in Arabidopsis reminiscent of the models for homeotic gene function derived from studies in Drosophila?

a) In both organisms, homeobox genes specify the identity of regions of the mature organism.

b) The key responsibility of the homeotic genes in both organisms is patterning of dorso-ventral asymmetry.

c) In both organisms, one homeotic gene is expressed at the two ends, a second expressed in to domains more central to that of the first, and a third expressed most centrally, thus contributing unambiguous identities to all regions of the organism.

d) In both organisms, the homeotic genes interact, so that it is often the combination of genes present that is critical in unambiguously specifying structures in the adult.

e) The ABC model of Arabidopsis is essentially identical to the Drosophila model for homeotic gene function, in that the Drosophila version of the A gene is abdominal-A, the Drosophila version of the B gene is Abdominal-B, and the Drosophila version of the C gene is Ultrabithorax.

Oxford University Press, Online Resource Centre, Chapter 06.

Chapter 06

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