A friend is interested in isolating genes that are expressed solely in liver cells but only has access to skin cells. She asks you for advice on whether to start her studies. What will you say?

Which of the following provides the strongest evidence for the conservation of tool-kit genes?

a. Bicoid moved from one fly embryo into the posterior of another fly embryo causes the formation of two head regions.

b. Mutation of an unrelated gene in another species of fly has a similar effect to mutation of bicoid in Drosophila.

c. A mouse Hox gene can be used to take over the function of a mutated Drosophila Hox gene.

d. Sheep can be cloned by fusing a differentiated adult cell with an enucleated egg.

In adult animals, ___________ are a source of undifferentiated cells that can divide to produce cells that can specialize.

A tool-kit gene is               .

The following predictions ask you to consider how genetic regulatory cascades provide positional information. Select True or False for each statement.

T/F Mutation of a gene at one level of a regulatory cascade will affect the expression of genes at all levels of the cascade.

T/F Mutation of a gene that is expressed later in a regulatory cascade will affect a smaller region of the body than mutation of gene that is expressed early in the cascade.

T/F In the regulatory cascade used by Drosophila, a gene at one level of the cascade will be controlled only by genes at the level immediately above it.

T/F Genes that control the largest regions of the Drosophila embryo are not transcribed in the embryo.

What is the connection between genetic regulatory cascades and the observation that differentiation is a step-by-step process?

What is a homeotic mutant?

a. An individual with a structure located in the wrong place

b. An individual with an abnormal head-to-tail axis

c. An individual that is missing segments

d. An individual with double the normal number of structures