Question 1 This question refers to development in...

Question 1 This question refers to development in Drosophila. A) Name and describe one maternal-effect gene that provides the initial information for the developing Drosophila embryo. B) What are the four classes of segmentation genes and what roles do they play in development? Briefly describe the roles and give one example of a gene in each of the 4 classes. Provide specific information on what each gene does. C) During what developmental stage of the Drosophila are homeotic genes expressed and what are their main functions? Give one example and discuss what its effect is, and how and why it is conserved in very divergent animals. D) If a fertilized Drosophila egg is punctured at the posterior end and a small amount of cytoplasm is allowed to leak out, what will be the most likely effect on the development of the fly embryo? Be specific as to the phenotypic effect, the gene(s) that would be involved, and the reasoning you used to predict the outcome you describe.

Transcript

00:01 For part a, take note that the fate map of the drosophila embryo along the dorsal axis at the blastetermine stage can be described as a series.

00:14 It is a series of longitudinal stripes.

00:22 The and ledge of the, we have the enlarge of the mesoderm is basically located mid -prudal.

00:36 Ventrally, followed by the broad region of the ventral and then dursal ectodermal analalogen.

00:45 Along the dursal midline, the anlogen of the rudimentary amniocerosa are located, although these anlogen are somewhat distorted in the head and tail region of the embryo.

00:58 In the large, segmented middle region of the embryo, they exhibit a clear parallel alignment.

01:04 And the formation of the dursal ventral pattern of the drosophila embryo depends on the activity of basically small number of maternal effect genes.

01:26 For this part, their phenotype and properties indicate that they are integrated into a single system which provides positional information for the developing embryo.

01:38 For part b, the timetable of drosophela development from egg to adult, where in the period of embryonic development begins at basically the fertilization and also takes about a day.

01:55 At the end of which the embryo hatches of the egg shell to become a larva, the larva then passes through three stages or in stars, separated by molds in which it sheds its old.

02:08 Coat of cuticle and lays down a larger one.

02:13 At the end of the third instar it pupates.

02:18 Inside the pupa a radical remodeling of the body takes place, a process of what we known as the metamorphosis.

02:30 Eventually about nine days after fertilization an adult fly or imago emerges.

02:36 The fly consists of a head with mouth, eyes, and antenna followed by the three thoracic segments, and eight or nine abdominal segments.

02:47 And each segment, although different from the others, is built according to a similar plan.

02:52 Segment t1, for example, carries a pair of legs, and t2 carries a pair of legs, a pair of legs plus a pair of wings.

03:10 And t3 carries, okay, it's carry, carries a pair of legs plus a pair of halteris.

03:35 Small knob -shaped balancers important in flight evolve from the second pair of wings that more primitive insects possesses...

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