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TLS Online TPP Program

#Question id: 7248

Planning of the Xenopus mesoderm along the dorso-ventral axis contains an antagonistic relationship between chordin and bmp-4. Is there an analogy here to dorso-ventral patterning in the Drosophila embryo?

#Unit 5. Developmental Biology
  1. Yes, the Drosophila homolog of Bmp-4, decapentaplegic (DPP), is antagonized by the Drosophila homolog of chordin, short gastrulation (SOG), in patterning of the dorso-ventral axis
  2. Yes, Drosophila also uses bmp-4 to specify ventral fates and chordin to specify dorsal fates
  3. Yes, the Drosophila dorsal protein is identical to the vertebrate bmp-4 protein, and specifies the ventral region of the embryo
  4. No. The closest analogy from Drosophila would be the antagonism between hunchback and nanos, but neither of those is signalling molecules, and they act to pattern the antero-posterior axis
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TLS Online TPP Program

#Question id: 34110

#Unit 2. Cellular Organization

A. DNA is wrapped 1.67 times around the histone octamer.
B. The structure of the DNA is altered so that it has an increased number of base pairs/turn in the middle, but a decreased number at the ends.
C. 0.6 negative turns of DNA are absorbed by the change in bp/turn from 10.5 in solution 
D. 10.2 bp/turn on the nucleosomal surface is linking-number paradox.

Find true and false
TLS Online TPP Program

#Question id: 34111

#Unit 2. Cellular Organization

A. 11-nm chromatin fibers consist of a string of nucleosomes.
B. 30-nm fibers have six nucleosomes/turn, which are organized into a two-start helix.
C. Histone H1, histone tails, and increased ionic strength all promote the formation of the 11-nm fiber.
D. Histone octamers are well conserved during replication, with H2A-H2B dimers and H32-H42 tetramers are.

Which of the correct combination of statements
TLS Online TPP Program

#Question id: 34112

#Unit 2. Cellular Organization

A. When interphase nuclei are suspended in a solution of low ionic strength, they swell and rupture to release fibers of chromatin.
B. Individual nucleosomes can be obtained by treating chromatin with the endonuclease micrococcal nuclease
C. When chromatin is digested with MNase, the DNA is cleaved into integral multiples of a unit length can be Fractionated by gel electrophoresis reveals the “ladder”
D. With MNase more than 95% of nuclear DNA can be recovered in the form of the 200-bp ladder.

Choose true and false
TLS Online TPP Program

#Question id: 34113

#Unit 2. Cellular Organization

Which of the following is incorrect statement 
TLS Online TPP Program

#Question id: 34114

#Unit 2. Cellular Organization

The tail of which histone/s is able to contact an H2A-H2B dimer in an adjacent nucleosome, which may contribute to the formation of higher order structures
TLS Online TPP Program

#Question id: 34115

#Unit 2. Cellular Organization

Choose correct statement