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TLS Online TPP Program

#Question id: 7135

Recently, it was reported that adult, differentiated cells can be made to behave as pluripotent stem cells by the introduction of a few genes, one of which was Oct4. What was the rationale for this experiment?

#Unit 5. Developmental Biology
  1. Oct4 expression is one of the requisites for the maintenance of pluripotent embryonic stem cells in culture.
  2. the Oct4 gene produces a cell-cell signaling protein that is used by stem cells to stimulate cell division
  3. Oct4 is only expressed in embryonic stem cells, and so its expression automatically reverses any differentiation that may have gone on in a cell
  4. the Oct4 gene is lost from differentiated cells through a genomic rearrangement, and its reintroduction reverses that rearrangement and hence differentiation
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TLS Online TPP Program

#Question id: 33908

#Unit 2. Cellular Organization

How is the linking number altered if one DNA strand is broken
TLS Online TPP Program

#Question id: 33909

#Unit 2. Cellular Organization

What is the Lk of a 5,000 bp circular duplex DNA molecule with a nick in one strand?
TLS Online TPP Program

#Question id: 33910

#Unit 2. Cellular Organization

What is the Lk of a 5,000 bp circular duplex DNA molecule after eight enzymatic turnovers by a single molecule of DNA gyrase in the presence of ATP?
TLS Online TPP Program

#Question id: 33911

#Unit 2. Cellular Organization

What is the Lk of a 5,000 bp circular duplex DNA molecule after eight enzymatic turnovers by a single molecule of DNA gyrase in the presence of ATP followed by 8 enzymatic turnovers by a single molecule of bacterial type I topoisomerase
TLS Online TPP Program

#Question id: 33912

#Unit 2. Cellular Organization

A. When a DNA molecule is negatively supercoiled, it is underwound. 
B. Any structural change involving DNA strand separation becomes more likely in negatively supercoiled DNA. 
C. Negative supercoiling makes establishment of left-handed Z-DNA in a segment of DNA 
D. The formation of plectonemic or solenoidal supercoils is favored as a means of negative supercoiling.

Find true and false
TLS Online TPP Program

#Question id: 33913

#Unit 2. Cellular Organization

A. Underwinding of a B-DNA helix might facilitate or stabilize the formation of Z-DNA.
B. Underwinding aids in the transition by providing a local region of unwound DNA that allows the shift to Z-DNA.
C. Overwinding of a B-DNA helix might facilitate or stabilize the formation of Z-DNA.
D. Overwinding aids in the transition by providing a local region of unwound DNA that allows the shift to Z-DNA.

What is correct combination of statements