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TLS Online TPP Program

#Question id: 4350

Portions of the DNA sequences of normal and mutant b-globin genes are shown. The most plausible explanation for why the indicated mutation (changing an A to a G) results in the disease b-thalassemia is that the mutation

#Unit 3. Fundamental Processes

  1. changes the amino acid specified by the codon of which the altered base is part

  2. generates a recognition site for a restriction enzyme, so the gene is cut in two

  3. creates a new splice site, so that a portion of the intron is not removed

  4. results in an increase in the transcription of the b-globin gene

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TLS Online TPP Program

#Question id: 15528

#Unit 4. Cell Communication and Cell Signaling

The B7 family of protein interact  with distinct receptor present on the T-cells, 
TLS Online TPP Program

#Question id: 15527

#Unit 4. Cell Communication and Cell Signaling

CD4 and CD8 T cells leave the thymus and enter the circulation as resting cells in which stage of the cell cycle?
TLS Online TPP Program

#Question id: 15526

#Unit 4. Cell Communication and Cell Signaling

If a thymocyte randomly generated a TCR with an affinity for MHC Class I, the TCR and CD8 would bind MHC Class I together, and generate a signal that specifically initiated a program that is 
a) silenced CD8 expression
b) silenced CD4 expression
c) induced expression of genes specific for helper T-cell lineage function
d) induced expression of genes specific for cytotoxic T-cell lineage function
TLS Online TPP Program

#Question id: 15525

#Unit 4. Cell Communication and Cell Signaling

In the instructive model, TCR/CD4 and TCR/CD8 coengagement generates unique signals, if a thymocyte randomly generated a TCR with an affinity for MHC Class I. which thymocyte would bind with MHC class I?
TLS Online TPP Program

#Question id: 15524

#Unit 4. Cell Communication and Cell Signaling

The bulk of DP thymocyte death (~95%) occurs among thymocytes that fail positive selection because 
TLS Online TPP Program

#Question id: 15523

#Unit 4. Cell Communication and Cell Signaling

The appearance of ϒδ thymocytes and αβ thymocytes during mouse fetal development. Fetal animals generate
a) more αβ T-cells than ϒδ T-cells
b) the proportion of ϒδ T-cells generated drops off dramatically after birth
c) the proportion of αβ T-cells generated drops off dramatically after birth
d) more ϒδ T-cells than αβ T cells