Question

1. The ste2 mutation is a defect in the:

	a.	Mating factor receptor
	b.	G Protein
	c.	Kinase complex
	d.	Cell arrest factor

2. Tight junctions ______________________.

	a.	Allow small, water-soluble molecules to pass from cell to cell
	b.	Interact with the intermediate filaments inside the cell.
	c.	Prevent the movement of molecules between cells.
	d.	Prevent the movement of molecules between cells.

3. A neuron and a white blood cell have very different functions. These differences are possible because: ______. (read carefully)

	a.	The proteins found in a neuron are completely different from the proteins found in a white blood cell.
	b.	The neuron and the white blood cell within an individual have different genomic DNA.
	c.	The neuron and white blood cells express different mRNAs and proteins.
	d.	Neurons and white blood cells do not need to transcribe and translate genes.

Answer 1

question 1

Mutations in six genes that eliminate responsiveness of Saccharomyces cerevisiae a cells to alpha-factor were examined by assaying the binding of radioactively labeled alpha-factor to determine whether their lack of responsiveness was due to the absence of alpha-factor receptors.

a. mating fator receptor

question 2

Tight junctions seal adjacent epithelial cells in a narrow band just beneath their apical surface. They consist of a network of claudins and other proteins. Tight junctions perform two vital functions: They limit the passage of molecules and ions through the space between cells.

c. prevent movement of molecules between cells.

question 3

c.The neuron and white blood cells express different mRNAs and proteins.

Every cell in the body contains the same DNA sequence and the same gene but all the genes are not expressed in a cell. Each cell expresses a particular set of genes according to the function they perform.

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