MCQs

The structural interaction of linker histone H1 with adjacent nucleosomes drives the further compaction of the 10-nm nucleosome strand into a 30-nm helical spiral loop array termed a solenoid.

Euchromatin is the transcriptionally active, loosely organized chromatin form that allows RNA polymerase complexes to access structural gene sequences. Heterochromatin represents tightly packed, silent regions.

Blocking the kinetochores prevents microtubule attachment at the centromere, interrupting mitotic checkpoints and halting orderly chromosome separation.

HAT enzymes add acetyl groups to basic lysine residues on histone tails, neutralizing their positive charges. This reduces their grip on DNA, transforming condensed heterochromatin into accessible euchromatin.

While total DNA and core structural histone quantities remain constant in a fixed G0/G1 somatic cell, the non-histone regulatory proteins, transcription factors, and active RNA transcripts shift dynamically with transcription levels.

The positive charges on histones neutralize the negative DNA backbone. Removing these charges disrupts the attractive forces, leading to chromatin de-condensation and a breakdown of higher-order chromosome packaging.

Telomerase maintains telomere length. Inhibiting it leaves the cell unable to synthesize telomeric repeats, causing progressive chromosome shortening with each replication cycle until cellular senescence is triggered.

Heterochromatin remains heavily condensed throughout the cell cycle and contains dense, methylated DNA sequences that are mostly transcriptionally silent.

Somatic chromosome consistency relies on high-fidelity DNA replication during S-phase followed by symmetrical separation of sister chromatids to daughter nuclei during mitosis.

Sub-metacentric chromosomes possess arms of unequal lengths due to sub-median centromeres, making them look like an 'L' during movement. Metacentric forms a 'V', and acrocentric forms a 'J'.

The kinetochore is a complex macromolecular protein structure assembled specifically on the centromeric DNA of each mitotic chromosome to bind spindle microtubules.

The sugar-phosphate backbone of DNA contains repeated phosphate groups that carry negative charges at physiological pH, allowing complementary electrostatic binding to basic histones.

The structural interaction of linker histone H1 with adjacent nucleosomes drives the further compaction of the 10-nm nucleosome strand into a 30-nm helical spiral loop array termed a solenoid.

Euchromatin is the transcriptionally active, loosely organized chromatin form that allows RNA polymerase complexes to access structural gene sequences. Heterochromatin represents tightly packed, silent regions.

A satellite body (or trabant) is a small chromosomal segment separated from the main body of the chromosome by a secondary constriction. Its presence characterizes SAT-chromosomes.

Metacentric chromosomes have a centrally located centromere, creating two arms of approximately equal structural length, taking on a characteristic 'V' shape during anaphase migration.

Histones are highly basic proteins because they contain large proportions of positively charged amino acids, specifically lysine and arginine. This positive charge mediates tight electrostatic interactions with the negatively charged sugar-phosphate backbone of DNA.

Secondary constrictions, also designated as Nucleolar Organizer Regions (NORs), contain specific genetic configurations responsible for transcribing ribosomal RNA and reorganizing the nucleolus.

Following replication in the S-phase, each chromosome at metaphase is composed of two identical copies called sister chromatids, which remain physically connected at the primary constriction site (centromere).