Question

Specify whether each of the statements below is

TRUE OR FALSE

and

EXPLAIN your reasoning

.

PLEASE NOTE: NO POINTS WILL BE AWARDED IF YOU DO NOT PROVIDE AN EXPLANATION

FOR YOUR CHOICE.

a. The effects of cyclic AMP vary depending on the cell type because different cells express different

isoforms of protein kinase A (0.4 points)

b. Binding of a ligand to a receptor tyrosine kinase activates the cytosolic catalytic domain of the

receptor by inducing a conformational change across the membrane through a single

transmembrane segment. (0.4 points)

You work in a developmental biology lab that uses

Xenopus laevis

(the African clawed frog) as a

model organism. You are working on a project investigating the activity of different cadherins in cells.

You insert a transgene to express RFP-E-cadherin (red) in neural crest cells from Xenopus embryos

and GFP-N-Cadherin in a second set of neural crest cells from Xenopus embryos. These cells do not

normally express ANY cadherins. Explain the results you expect to see in the following cultures.

a. Culture A: cells that express RFP-E-cadherin (0.3 points)

b. Culture B: A mixture of cells expression RFP-E-cadherin and GFP-N-Cadherin-expressing cells

(0.4 points)

c. Culture C: cells that express RFP-E-cadherin which have been transfected with an siRNA to

knock-down the gene that codes for fibronectin (0.4 points)

d. Culture D: Cells that express GFP-N-cadherin grown in the presence of EGTA, a compound that

depletes free Ca

2+

concentration from the culture medium (0.4 points)

Answer 1

1. True - In intracellular signaling triggers cAMP is activation of PKA. In mammals two major types of PKA (PKA I and II) are present. In addition, four different isoforms, two of RI (RI? and RI?) and two of RII (RII? and RII?), each encoded by a separate gene. All of these PKA isoforms are characterized by different subcellular localization and tissue distribution.

2. True - RTKs are single-pass, type I receptors resident in the plasma membrane. Generally, RTKs are activated through ligand-induced oligomerization, typically dimerization, which juxtaposes the cytoplasmic tyrosine kinase domains.

A. The cells express RFP-E-cadherin appears red in color.
B. A mixture of cells expression RFP-E-cadherin and GFP-N-Cadherin-expressing cells express both Red and green inside the cells.
C. siRNA to knock-down the gene that codes for fibronectin leads to N-cadherin was concentrated along areas of
cell-cell contact in confluent monolayers devoid of fibronectin. So, N-cadherin Red stain localizes to cell-cell
contacts at cell borders.
D. Calcium chelator (EGTA) to disrupt the adhesive interaction, cells not contact with each other. Green fluroscence express inside the cells.