Mutations that block expression of the E-cadherin gene are thought to be an important step in metastasis. To better understand how loss of E-cadherin contributes to metastasis, scientists created two cell lines that differed in their expression of E-cadherin. One cell line expressed normal E-cadherin, but at 10% of the usual levels. The other cell line expressed normal E-cadherin at the usual levels, and also, at high levels a mutant form that included the cytoplasmic domain but lacked the rest of the protein. Both cell lines exhibited strongly reduced cell adhesion in culture. However, only the cell line with reduced expression of normal E-cadherin metastasized when introduced into mice.

Which of the following hypotheses is most consistent with the observations on cell adhesion and metastasis in these cell lines?

#Question id: 20337

#Unit 12. Applied Biology

#Question id: 4686

#Unit 3. Fundamental Processes

Bacteriophage λ, has two mode of life cycle;  lytic and lysogenic.  In the lytic growth

a) a single Cro dimer is bound to OR3; this site overlaps PRM and so Cro represses that promoter

b) Repressor bound at OR1 and OR2 blocks RNA polymerase binding at PR, repressing transcription from that promoter

c) PR and PL binds RNA polymerase and directs transcription of lytic genes

d) During lytic, PRM is on while PR (and PL) are off

Find the correct combinations of lytic growth.

#Question id: 12327

#Unit 10. Ecological Principles

#Question id: 7764

#Unit 5. Developmental Biology

Cellular senescence may have evolved to protect organisms against cancer. Instead of dividing out of control, the cells die. Cellular senescence appears to be regulated by several tumor suppressor genes, especially p53.what is the most appropriate reason behind this,

1) Transcription factor p53 is thought to suppress tumorigenesis by causing cell arrest and senescence in response to short telomeres, DNA damage, and viral or external signals to divide

2) This factor can stop the cell cycle, cause cellular senescence in rapidly dividing cells, instruct genes to initiate cellular apoptosis, and activate DNA repair enzymes.

3) Induction of apoptosis or cellular senescence by p53 always beneficial.

#Question id: 19098

#Unit 4. Cell Communication and Cell Signaling