All animals with eyes or eyespots that have been studied so far share a gene in common. When mutated, the gene Pax-6 causes lack of eyes in fruit flies, tiny eyes in mice, and missing irises (and other eye parts) in humans. The sequence of Pax-6 in humans and mice is identical. There are so few sequence differences with fruit fly Pax-6 that the human/mouse version can cause eye formation in eyeless fruit flies, even though vertebrates and invertebrates last shared a common ancestor more than 500 million years ago.

The appearance of Pax-6 in all animals with eyes can be explained in multiple ways. Based on the information above, which explanation is most likely?

#Question id: 7276

#Unit 5. Developmental Biology

The cells that make up a tetrapod limb arise from three developing tissues:

The ____a______ will provide skeletal precursors to the limb.

The _____b____ will provide muscle precursors to the limb.

The _____c____ will provide the skin of the limb.

Which of the following option is correct?

#Question id: 7275

#Unit 5. Developmental Biology

The following experiment is designed to study the role of several hormones in the regulation of metamorphosis in frogs.

If the thyroid gland were removed from the tadpoles in Group 4, metamorphosis would

#Question id: 7274

#Unit 5. Developmental Biology

The following experiment is designed to study the role of several hormones in the regulation of metamorphosis in frogs.

 If the thyroid gland were removed from the tadpoles in Group 3, metamorphosis would

#Question id: 7273

#Unit 5. Developmental Biology

Hox9 and Hox10 paralogues specify the stylopod, Hox11 paralogues specify the zeugopod, and Hox12 and Hox13 paralogues specify the autopod. This scenario has been confirmed by numerous experiments.

Which of the following experiment correctly describe this scenario?

#Question id: 7272

#Unit 5. Developmental Biology

Few statements regarding the role of disheveled (dsh) and beta-catenin in the development of sea urchin.

A. beta-catenin accumulates predominantly in the macromeres and somewhat in veg2 tier cells.

B. At the fourth cleavage disheveled and β-catenin, both of which are found in the cytoplasm and are inherited by the micromeres.

C. Treating sea urchin embryos with lithium chloride allows β-catenin to accumulate in every cell and transforms presumptive ectoderm into endoderm.

D. When β-catenin is prevented from entering the nuclei (i.e., it remains in the cytoplasm), the vegetal cell fates are specified, and the entire embryo develops as a ciliated ectodermal ball.

Which one of the following options represents a combination of correct statement?

#Question id: 7271

#Unit 5. Developmental Biology

In drosophila, Head formation required higher Bicoid concentrations than thorax formation, because