MCQs

Inhibiting HDAC keeps histones acetylated, neutralizing their positive charges and keeping chromatin open (euchromatin) to boost transcription.

Without a functional termination response, the polymerase runs past the end of the gene, creating a long, un-terminated read-through transcript.

Intercalating agents distort the helix by stretching the backbone, which tricks DNA polymerase into inserting or omitting bases, causing frameshift mutations.

Huntington's disease is a classic trinucleotide repeat disorder where a CAG expansion in the HTT gene produces a toxic, polyglutamine-expanded huntingtin protein.

Z-DNA is a left-handed helical variant with a zigzag sugar-phosphate backbone, favored by repeating purine-pyrimidine steps, high salt, or methylation.

Unwinding the helix creates torsional strain and positive supercoils ahead of the moving polymerase; without topoisomerase to relieve this stress, transcription stalls.

The linear sequence of nucleotide codons inside exons determines the exact order of amino acids added during protein translation.

Each phosphate group in the phosphodiester backbone loses a hydrogen atom at cellular pH, giving the exterior of the DNA a negative charge.

Thymine is a pyrimidine base specific to DNA, whereas RNA uses uracil as the complementary partner for adenine.

The mass of a gene depends on its length; longer nucleotide sequences contain more base pairs, increasing the total molecular weight.

Enhancers are regulatory DNA sequences that bind activator proteins, interacting with the promoter to boost transcription.

The Watson-Crick model shows DNA as a right-handed double helix, where two complementary strands twist around a central longitudinal axis.

A premature stop codon halts translation early, yielding an incomplete, truncated polypeptide chain that is usually non-functional.

Eukaryotic chromosomes are highly organized nucleoprotein complexes made of a single linear DNA molecule wound around structural histones.

Electrostatic hydrogen bonds form between the partially positive hydrogen atoms and partially negative oxygen or nitrogen atoms of matching bases.

Silent mutations alter the codon sequence without changing the translated amino acid, leaving the protein's function uncompromised.

The terminator is a distinct downstream regulatory sequence that signals RNA polymerase to stop transcription and detach.

Because the genetic code is nearly universal, organisms share the same codon-to-amino acid rules, making recombinant DNA tech possible.

Ribosomes serve as the structural and catalytic factories where tRNA molecules match codons to assemble amino acids into a protein.