a) What is the role of the Hox genes in animal development and what types of phenotypes do you see in mutations of Hox genes? Provide an example of a mutant phenotype of a Hox gene in Drosophila. 3mrks The Hox genes are known to act in combination. Panel A in figure below shows the normal expression patterns of the bithorax complex, and segments that align with the expression patterns. Panel B shows the segmental phenotypes in mutants for both abdominal - A and Abdominal - B, panel C shows the phenotypes in mutants for Abdominal - B, and panel D shows the phenotypes in mutants for Ultrabithorax. b) Describe how the segmental phenotypes illustrate the combinatorial action of Hox genes (you can ignore A9 as it is patterned by the terminal patterning system). 4mrks A) Parasegments 11 12 13 14 B) D) 10 11 12 13 14 Segments A2 A3 A4 A5 Abdominal-B abdominal-A Ultrabithorax T1 12 13 A1 11 12 12 12 A2 A3 A4 A

Pax6 is a gene that is involved in mammalian eye development. Mutations in this gene result in a lack of iris in humans, and mice that are homozygous for the mutation lack eyes completely. Mutations in the eyeless gene in the fruitfly Drosophila result in reduced eyes. Expressing Pax6 from mammals in other tissues of Drosophila during its embryonic development can result in an ectopic eye (e.g. an eye expressed in a different tissue type). An example of an ectopic eye on the antenna of Drosophila is shown below. Part A:  The eye of humans, mouse, and fly are an example of the following (check all that apply)  A. Structural analog    B. Structural homolog    C. Developmental homolog    D. Genetic homolog   Part B:  Darwin's hypothesis of natural selection has two components: Species are not static but change through time Species are related, and not independent. In what ways does the human, mouse, and fly eye support or contradict one or both of the two components of…

describe the arrangment of Hox genes on each chromosome in mammals in relation to their expression pattern. What effect would you expect if you expressed a Hox gene more anterior to its normal expression domain?

As shown in Figure 13-26, the Sonic hedgehog gene is expressed in many places in a developing chicken. Is theidentical Sonic hedgehog protein expressed in each tissue? If so, how do the tissues develop into different structures? If not, how are different Sonic hedgehog proteinsproduced?