MCQs

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.

Having fewer hydrogen bonds makes A-T rich regions easier to unzip, which is why replication origins and promoters are rich in A-T pairs.

B-DNA is the standard, stable conformation adopted by native DNA molecules inside the aqueous environment of living cells.

A cistron is a genetic unit defined by the cis-trans position test, matching the DNA sequence needed to build one polypeptide.

The wider, deeper gap on the outside of the helix is the major groove, which provides easy access for sequence-specific DNA-binding proteins.

DNA methyltransferases add a methyl group to the carbon-5 position of cytosine rings, a key modification for silencing gene expression.

Without a functional promoter sequence, RNA polymerase cannot locate or bind the gene, shutting down transcription entirely.

Enclosing the genetic bases within the hydrophobic core protects the fragile hereditary codes from reactive molecules in the cytoplasm.

By showing that viral DNA (32P) enters the host cell while viral protein (35S) stays outside, they proved DNA is the hereditary material.

The template strand runs anti-parallel and complementary to the coding strand, making the matching sequence 3'-TACGTT-5'.

The spliceosome is a large ribonucleoprotein complex that removes introns and splices exons together to form mature mRNA.

The total cross-sectional width of the standard B-form DNA double helix is 2.0 nm (20 A˚).

With 61 codons coding for 20 amino acids, most amino acids are specified by more than one triplet codon, making the code degenerate.