BIO NMDCAT

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

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

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

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

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.

Ribosomes serve as the structural and catalytic factories where tRNA molecules match codons to assemble amino acids into a protein.

Pairing purines with pyrimidines preserves a constant 2 nm spacing, preventing structural bulges or pinches along the helix.

Heating a DNA sample provides enough thermal energy to break the hydrogen bonds and base-stacking interactions, separating the strands.

An operon is a functional genetic unit found in bacteria that allows several genes in a shared pathway to be transcribed together as a single mRNA.

Lacking a 2'-OH group allows deoxyribose to prefer a C2'-endo sugar pucker, which drives the flexible, uncrowded B-DNA geometry.

Coined by Francis Crick, the Central Dogma outlines the unidirectional transfer of functional sequence information during gene expression.

A locus refers to the fixed geographic coordinate or position where a gene or genetic marker resides on a chromosome.

To form proper hydrogen bonds across the core, the twin strands must line up in opposite orientations, pairing a 5' end with a 3' end.

Alleles are alternative nucleotide variants of a gene found at the same chromosomal locus, governing variations of the same trait.

Each G-C pair has three hydrogen bonds (5×3=15) and each A-T pair has two (3×2=6). The total is 15+6=21.

Silent mutations take advantage of the redundancy of the genetic code, where multiple codons translate into the same amino acid.

The structural framework of the DNA strand is formed by a repeating chain of deoxyribose sugars linked by neutral phosphodiester groups.

The TATA box is a critical promoter element situated upstream of the transcription start site, helping position RNA polymerase II.

DNA replication is the semi-conservative duplication of the cellular genome, ensuring each daughter cell inherits a complete set of genes.