MCQs

The non-template strand matches the mRNA transcript sequence exactly (except that DNA has T where RNA has U), earning it the name "coding strand."

The nucleosome is the primary structural unit of chromatin, packing a 147-base-pair segment of DNA around a histone octamer core.

Inserting or deleting a base shifts the triplet reading frame downstream, completely altering the remaining amino acid sequence.

Each phosphate group in the backbone retains a negative charge at physiological pH by releasing a hydrogen ion (H+), acting as an acid.

By convention, the coding strand is written 5' to 3' because the ribosome reads mRNA 5' to 3' to build a protein from its N- to C-terminus.

The B-DNA helix has a pitch of 3.4 nm and a base-pair step of 0.34 nm, accommodating roughly 10 base pairs per full turn.

Exons are the coding segments of a gene that remain in the mature mRNA transcript after splicing, carrying the blueprint for translation.

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.