MCQs

Structural genes carry the specific nucleotide blueprints required to assemble amino acids into a polypeptide chain on a ribosome.

Cytosine and thymine are single-ring pyrimidines, whereas adenine and guanine are double-ring purines.

A codon is a triplet of bases that specifies a particular amino acid or a stop signal during protein translation.

One complete helical turn spans a longitudinal length of 3.4 nm (34 A˚) and contains approximately 10 base pairs.

Chargaff’s rules dictate that [A]=[T] and [G]=[C]; therefore, the sum of purines (A+G) must equal the sum of pyrimidines (T+C).

Rosalind Franklin’s famous "Photo 51" obtained via X-ray crystallography revealed the helical configuration and dimensions of the DNA molecule.

Phosphodiester bonds covalently link the 3' carbon of one deoxyribose sugar to the 5' carbon of the adjacent sugar via a phosphate group.

The double helix maintains a constant width of 2 nm (20 A˚) because a double-ringed purine always pairs with a single-ringed pyrimidine.

Adenine (a purine) always pairs with thymine (a pyrimidine) using two hydrogen bonds in standard Watson-Crick base pairing.

The 5' end of a DNA or RNA strand terminates in a phosphate group attached to the 5' carbon of the pentose sugar.

A gene is the fundamental structural and functional unit of heredity, consisting of a nucleotide sequence that carries the code for a protein.

Guanine pairs with cytosine via three hydrogen bonds, creating a more thermally stable bond than the adenine-thymine pair.

One strand runs in the 5' to 3' direction while its complementary partner runs in the 3' to 5' direction.

Retinal links to the opsin protein via a carbon-nitrogen double bond called a Schiff base linkage, which is central to proton-pumping mechanisms.

AGEs are formed via glycation, a chaotic, non-enzymatic reaction where excess blood sugars bind randomly to proteins and lipids, disrupting their function.

MTP is essential for transferring lipids onto the emerging ApoB-100 polypeptide chain; a deficiency in MTP results in the disorder abetalipoproteinemia.

The host immune receptor TLR4 identifies the specific configuration of Lipid A's six fatty acid chains; altering this number prevents effective receptor binding and signaling.

Autoimmune attacks targeting myelin glycolipids or associated proteins disrupt the structural layout of the myelin sheath, impairing nerve signal conduction.

Sialic acid residues carry a negative charge at physiological pH; removing them lowers the cell's negative charge, altering cell-to-cell spacing and interactions.