Molecular Basis of Inheritance

Flashcards covering the molecular structure of DNA, its packaging, and discovery as genetic material based on the provided lecture notes.

DNA

A long polymer of deoxyribonucleotides that serves as the genetic material in most organisms.

$\times 174$ bacteriophage

A bacteriophage that contains $5386$ nucleotides.

Bacteriophage lambda

A virus featuring $48502\,bp$ (base pairs) in its genetic sequence.

Escherichia coli

A bacterium with a DNA length of $4.6 \times 10^{6}\,bp$.

Haploid human DNA

The human genetic content in a single set of chromosomes, totaling $3.3 \times 10^{9}\,bp$.

Nucleotide

A chemical unit composed of a nitrogenous base, a pentose sugar (ribose or deoxyribose), and a phosphate group.

Purines

A category of nitrogenous bases that includes Adenine and Guanine.

Pyrimidines

A category of nitrogenous bases that includes Cytosine, Uracil, and Thymine.

N-glycosidic linkage

The bond linking a nitrogenous base to the $OH$ of $1'C$ pentose sugar to form a nucleoside.

Phosphoester linkage

The bond connecting a phosphate group to the $OH$ of $5'C$ of a nucleoside.

$3'-5'$ phosphodiester linkage

The linkage that joins two nucleotides together to form a dinucleotide or polynucleotide chain.

Nuclein

The name given to the acidic substance identified in the nucleus by Friedrich Meischer in 1869.

Erwin Chargaff's Rule

The observation that for double-stranded DNA, the ratios between Adenine and Thymine and Guanine and Cytosine are constant and equal one.

Anti-parallel polarity

The structural arrangement where one polynucleotide chain runs $5' \rightarrow 3'$ and the other runs $3' \rightarrow 5'$.

Pitch of the helix

The length of one full turn of the DNA double helix, measuring $3.4\,nm$.

Central dogma

Francis Crick's proposition that genetic information flows from $\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$.

Nucleoid

A region in prokaryotes like E. coli where negatively charged DNA is held by positively charged proteins in large loops.

Histones

Positively charged, basic proteins rich in lysine and arginine residues used to package DNA in eukaryotes.

Histone octamer

A unit consisting of eight histone molecules that forms the core of a nucleosome.

Nucleosome

A structure formed by wrapping negatively charged DNA around a positively charged histone octamer, typically containing $200\,bp$.

Chromatin

Repeating units of nucleosomes appearing as 'beads-on-string' that form thread-like stained bodies in the nucleus.

NHC proteins

Non-histone Chromosomal proteins required for the packaging of chromatin at higher levels.

Euchromatin

Loosely packed, lightly staining chromatin that is transcriptionally active.

Heterochromatin

Densely packed, darkly staining chromatin that is transcriptionally inactive.

Transforming Principle

The concept derived from Frederick Griffith's experiments in 1928, where heat-killed S strain bacteria changed the physical form of live R strain bacteria.