BIO NMDCAT

XP is caused by defects in the NER pathway, which is responsible for cutting out UV-induced pyrimidine dimers and bulky DNA distortions.

G-C pairs are bound by three hydrogen bonds, meaning G-C rich fragments require higher temperatures to denature than A-T rich sequences of the same length.

Mutilating a splice site prevents the spliceosome from recognizing the intron-exon boundary, leading to intron retention or exon skipping during splicing.

Polymerization relies on the cleavage of pyrophosphate (PPi​→2Pi​) to provide the forward driving force; blocking this halts the reaction.

NMD is a surveillance mechanism that detects premature stop codons on transcripts and degrades them, preventing the accumulation of toxic, truncated proteins.

Because the glycosidic bonds project unevenly, the backbones wind asymmetrically around the axis, creating alternating major and minor grooves.

The Shine-Dalgarno sequence base-pairs with the 16S rRNA of the 30S subunit, aligning the bacterial ribosome with the start codon to initiate translation.

Hypoxanthine pairs with cytosine, meaning the original template A-T pair becomes a G-C pair after a few rounds of replication, causing a transition mutation.

Triple-stranded H-DNA forms when a third single strand winds into the major groove of a duplex, binding via alternative Hoogsteen hydrogen bonds.

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

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

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

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

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

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

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

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

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

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