Practice Questions

TLS Online TPP Program

#Question id: 5670

Embryonic stem cells can be induced in the laboratory to differentiate into muscle, nerve, pancreatic, and other specialized cell types. It has recently become possible to trigger the dedifferentiation of somatic cells back into pluripotent cells (so-called induced pluripotent stem cells or iPS cells) by artificially enhancing the production of a relatively small number of key transcriptional factors known to be required for maintenance of pluripotency. Examples of such transcription factors are OCT4 and NANOG. The production of OCT4 and NANOG (and other key regulatory proteins) is stimulated by a transcription factor known as FOXP1, a member of the Forkhead family of DNA-binding proteins. There are two isoforms of FOXP1.

Which of the following statement regarding to FOXP1 is incorrect?

#Unit 5. Developmental Biology

The protein encoded by the exon 18b–carrying mRNA is called FOXP1-ES: this activates genes (OCT4, NANOG, etc.) that promote dedifferentiation, and thus stimulates iPS cell formation.
In the exon 18a–containing form encodes FOXP1 itself, and this has the opposite effect: it fails to stimulate expression of OCT4 and NANOG and instead actives genes that promote differentiation.
FOXP1 binds to DNA via a domain known as a Winged helix, which recognizes a particular DNA sequence.
The switch from exon 18a to exon 18b substitutes 3 residues in the Winged helix region of the protein including six amino acids that are known to contact DNA.

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TLS Online TPP Program

#Question id: 34109

#Unit 2. Cellular Organization

A. The chromocenter of polytene chromosome consists largely of heterochromatin

B. The chromocenter of polytene chromosome that consists largely of euchromatin

C. Chromocenter is all four chromosomes of D. melanogaster aggregate

D. Polytene chromosome are formed by a process known as endoreduplication

Which combination of statement is correct

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