Which kind of DNA should provide the best molecular clock for gauging the evolutionary relatedness of several species whose common ancestor became extinct billions of years ago?

#Question id: 7266

#Unit 5. Developmental Biology

After brief examination of the evolution of the tetrapod limb, from fish fins to human hands, has hopefully illuminated the importance of Hox gene regulation during limb development. Hox genes are critical for:

#Question id: 7265

#Unit 5. Developmental Biology

Following statement regarding to the cascade of regulated RNA splicing controls drosophila sexual differentiation.

A. The Sex-lethal (Sxl) protein, encoded by the sex-lethal gene, is the first protein to act in the cascade and present only in female embryos.

B. Early in development, the Sxl gene is transcribed from a promoter that functions only in male embryos.

C. Later in development, this male-specific promoter is shut off, and another promoter for sex-lethal becomes active in both male and female embryos.

D. In male embryos, however, in the absence of early Sxl protein, exon 3 of the sex-lethal pre-mRNA is spliced to exon 2 to produce an mRNA that contains a stop codon early in the sequence.

Which of the following is correct?

#Question id: 7264

#Unit 5. Developmental Biology

The Dictyostelia social amoebas are found in a wide range of soil habitats. They can come together to form a fruiting structure, in which a proportion of cells are sacrificed to build the stalk and the remainder differentiate into resilient dormant spores. This multicellular life cycle is common to all Dictyostelids. It consists of an interconnected programme of cell movement and cell differentiation, and has been intensively studied in the model organism D. discoideum. Few mutants (Column A) and phenotypes (Column B) are listed in the table given below.

 Match the correct mutant with the observed phenotype.

#Question id: 7263

#Unit 5. Developmental Biology

Following statements are regarding to the drosophila.

 A. At the completion of oogenesis, the bicoid message is anchored at the anterior end of the oocyte and the nanos message is tethered to the posterior end in translationally dormant condition.

 B. The translation inhibitors Smaug and CUP. Smaug binds to the 3’UTR of both bicoid and nanos mRNA and recruits the CUP protein that prevents the association of the message with the ribosome as well as recruiting other proteins that deadenylate the message and target it for degradation.

 C. The bicoid-Exuperantia complex is transported out of the nurse cells and into the oocyte via microtubules (Kinesin ATPase).

 D. Two other maternally provided mRNAs—caudal and hunchback are critical for patterning the anterior and posterior regions of the body plan, respectively.

 Which of the following combination is correct?

#Question id: 7262

#Unit 5. Developmental Biology

Match the following Gene (column I) with their function (column II).

Which of the following is correct?

#Question id: 7260

#Unit 5. Developmental Biology

There are maternally-determined variations along the animal-vegetal axis that are necessary for normal development in sea urchin. Which of the following statements about regulation in sea urchin embryos is consistent with that fact?