A female fly, full of fertilized eggs, is swept by high winds to an island far out to sea. She is the first fly to arrive on this island, and the only fly to arrive in this way. Thousands of years later, her numerous offspring occupy the island, but none of them resembles her. There are, instead, several species each of which eats only a certain type of food. None of the species can fly, for their flight wings are absent, and their balancing organs (i.e., halteres) are now used in courtship displays. The male members of each species bear modified halteres that are unique in appearance to their species. Females bear vestigial halteres. The ranges of all of the daughter species overlap.In each fly species, the entire body segment that gave rise to the original flight wings is missing. The mutation(s) that led to the flightless condition could have

#Question id: 7311

#Unit 5. Developmental Biology

According to the ABC model of flower development in Arabidopsis, three classes of organ identity genes— designated A, B, and C— are required to specify the identity of floral organs in each whorl of a flower. If wild type Arabidopsis were transformed with a chimeric gene composed of a C class promoter fused to a B class coding sequence, which of the following arrangements   (outer to inner) would be predicted?

#Question id: 7309

#Unit 5. Developmental Biology

Following statements are regarding to the molecular basis of the coincidence model in Arabidopsis.

A. In Arabidopsis under short days, there is little overlap between CO mRNA expression and daylight.

B. CO protein does not accumulate to sufficient levels in the phloem to promote the expression of the transmissible floral stimulus and the plant remains vegetative.

C. Under long days, the peak of CO mRNA abundance (at hours 12 through 16) overlaps with daylight (sensed by phyA and cryptochrome [cry]), allowing CO protein to accumulate.

D. CO activates FLC mRNA expression in the phloem, which causes flowering when the FT protein is translocated to the apical meristem.

Which of the following is incorrect?

#Question id: 7308

#Unit 5. Developmental Biology

In Arabidopsis thaliana, the transition to flowering involves multiple factors, pathways and meristem identity genes. Following statements regarding to the mechanism and function of meristem identity genes.

 A. FT mRNA is expressed in companion cells of the leaf vein in response to multiple signals, including day length, light quality, and temperature.

 B. The FT–FD complex activates AP1 in the inflorescence meristem and SOC1 in the floral meristem, which triggers LFY gene expression.

 C. LFY and AP1 trigger expression of the floral homeotic genes.

 D. FLC acts as a negative regulator of SOC1 in the meristem and as a negative regulator of FT in the leaves.

 Which of the following is incorrect?

#Question id: 7306

#Unit 5. Developmental Biology

A plant scientist was hired by a greenhouse operator to devise a way to force iris plants to bloom in the short days of winter. Iris normally blooms as a long-day (short-night) plant. Which of the following has the best chance of creating iris blooms in winter?

#Question id: 7304

#Unit 5. Developmental Biology

Which one of the following will be observed when auxin to cytokinin ratio is increased in the culture medium during organogenesis from tobacco pith callus?

#Question id: 7303

#Unit 5. Developmental Biology

The ‘quartet model’ explains how the protein products of the ABCE-function genes might interact to control floral organ identity. Following statements are based on this model. Which one of them is incorrect?