MCQs

An N-glycosidic bond connects the 1' carbon of the pentose sugar to the nitrogen atom at position 1 in pyrimidines or position 9 in purines.

Pleiotropy happens when a single gene codes for a protein used in multiple tissues, meaning a mutation can cause widespread symptoms.

Hydrogen bonds are weak non-covalent interactions, allowing the twin strands to unzip easily when driven by specialized enzymes.

A missense mutation alters a single nucleotide, changing a codon so that it incorporates a different amino acid into the protein.

The promoter is a specific upstream nucleotide sequence that signals the transcription machinery where to start making RNA.

Placing the charged, polar groups on the outside allows DNA to interact favorably with the watery environment of the nucleoplasm.

Human genes contain introns, which bacteria cannot slice out because they lack spliceosomes, leading to a flawed, non-functional protein.

DNA polymerases require a free 3'-OH group to form a phosphodiester bond with the 5' phosphate group of an incoming dNTP.

Transcription generates an RNA transcript that is complementary and anti-parallel to the DNA template strand, swapping thymine for uracil.

Introns are intervening, non-translated sequences within a gene that are transcribed into pre-mRNA but removed by splicing.

G-C pairs are linked by three hydrogen bonds, which require more thermal energy to disrupt than the two hydrogen bonds holding A-T pairs together.

With 10 base pairs per complete helical turn of 3.4 nm, the step distance between consecutive base pairs is 3.4/10=0.34 nm.

Purines are double-ringed; pairing two purines would exceed the 2 nm diameter, while pairing two pyrimidines would make the helix too narrow.

The hydrophilic sugar-phosphate backbones face the aqueous exterior, while the nitrogenous bases point inward to hide from water and form pairs.

Refined by Beadle and Tatum, and later updated to "one gene-one polypeptide," this concept binds a genetic locus to a single protein product.

The glycosidic bonds do not project directly opposite one another, making the spaces between the backbones unequal around the cylinder.

If A=30%, then T=30%, totaling 60%. The remaining 40% is split equally between Guanine (20%) and Cytosine (20%).

While hydrogen bonds hold the pairs together horizontally, vertical base-stacking interactions insulate the hydrophobic bases from water.

The 3' end of a nucleic acid strand terminates at the third carbon of the sugar ring, which carries a free hydroxyl group.