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

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.

Locate fluorine (F) on the partial periodic table provided in Figure 2.2. Predict its relative electronegativity compared to hydrogen, sodium, and oxygen. State the number and type of bond(s) you expect it would form if it reacted with sodium (Na).

Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior larval body parts and mirror-image duplication of posterior parts. This is evidence that the product of the bicoid genea. normally leads to formation of head structures.b. normally leads to formation of tail structures.c. is transcribed in the early embryo.d. is a protein present in all head structures.

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

What is 'selected' during natural selection? Explain your answer.

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.

DRAW IT Each blue circle in the figure below represents a cell in a cell lineage. Draw two modified versions of the cell lineage so that each version produces three cells. Use apoptosis in one of the versions, marking any dead cells with an X.

PROCESS OF SCIENCE Explain why researchers formulate a null hypothesis in addition to a hypothesis when designing an experimental study.