Practice Questions

TLS Online TPP Program

#Question id: 2897

The transcription of most protein coding genes in mammals (~70 percent) occurs at a lower rate than at TATA box–containing and initiator-containing promoters and begins at any of several alternative start sites within regions of about 100–1000 bp that have an unusually high frequency of CG sequences. Which one of the following best explains it?

#Unit 2. Cellular Organization

CG-rich sequences are bound by histone octamers more tightly than CG-poor sequences because less energy is required to bend around the histone octamer forming a nucleosome.
During housekeeping gene expression, the enzyme methyltransferase is temporarily silenced by miRNA, thus shutting down global methylation.
As soon as the cytosine is methylated in the promoter region, the enzymes of DNA repair pathways remove the methyl group, thereby ensuring gene expression.
A remarkable feature of the CpG islands is that transcription from these elements is initiated in both directions, even though only transcription of the sense strand yields an mRNA.

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TLS Online TPP Program

#Question id: 34106

#Unit 2. Cellular Organization

Isolated telomeric fragments do not behave as though they contain single-stranded DNA; instead, they show aberrant electrophoretic mobility due to

TLS Online TPP Program

#Question id: 34107

#Unit 2. Cellular Organization

A. Lampbrush chromosomes are formed during an unusually extended mitosis

B. The lampbrush chromosomes are meiotic bivalents, each consisting of paired homologous chromosomes that have been replicated

C. The lampbrush chromosomes are held together only by chiasmata that indicate points of chromosome crossover.

D. The loops around Lampbrush are surrounded by a matrix of ribonucleoproteins that contain nascent RNA chains.

TLS Online TPP Program

#Question id: 34108

#Unit 2. Cellular Organization

What is order of steps to visualise Individual bands containing particular genes can be identified by in situ hybridization.

A. Target cells squashed on slide and freeze in dry ice

B. Wash with ethanol

C. Dip in agar solution

D. Denature DNA

E. Add radioactive probe

F. Wash off unreacted probe

G. Autoradiography

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