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.

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).

Histone H1 is distinct from the core octamer proteins; it functions as the linker histone that binds to the entry/exit site of DNA on the nucleosome core particle, facilitating higher-order folding into the 30-nm solenoid fiber.

A nucleosome is the fundamental repeating structural unit of chromatin, consist of approximately 146 base pairs of DNA wrapped around a core octamer of basic histone proteins (two copies each of H2A, H2B, H3, and H4).

Telomeres are highly specialized, non-coding repetitive DNA sequences found at the terminal tips of linear chromosomes that protect them from degradation and end-to-end fusion.

Telocentric chromosomes exhibit a centromere at the absolute terminal end, resulting in a single visible arm. Metacentric has a central centromere, sub-metacentric has a slightly off-center centromere, and acrocentric has a near-terminal centromere.

The centromere represents the primary constriction site of a chromosome. It serves as the assembly platform for the kinetochore complex where mitotic or meiotic spindle fibers attach. Telomeres are terminal ends, and satellite bodies are associated with secondary constrictions.

Eukaryotic chromosomes are biochemically composed of chromatin material, which primarily consists of deoxyribonucleic acid (DNA) complexed with highly basic histone proteins. Other options represent different cellular macromolecules not forming the core structural composition of chromosomes.

Premature electron transfers to oxygen at complexes I and III form superoxide radicals, making the mitochondrion the chief producer of intracellular ROS.

Electron flow drives complexes I, III, and IV to pump protons out of the matrix into the intermembrane space, creating a reservoir of high proton concentration.

Porins render the outer membrane freely permeable to small molecules and metabolic substrates, unlike the highly selective inner membrane.

The conversion of amino acid carbon skeletons into metabolic intermediates like alpha-ketoglutarate requires enzymes located within the mitochondrial matrix.

The TIM23 complex is the primary translocase channel that threads unfolded precursor proteins across the inner mitochondrial membrane into the matrix.

Paternal mitochondria entering the egg are tagged with ubiquitin and selectively destroyed via mitophagy, ensuring that only maternal mitochondrial DNA survives.