Genetic Material, DNA Replication, and Repair

Comprehensive vocabulary flashcards covering the discovery, structure, topology, and human genomics of DNA, as well as eukaryotic DNA replication and repair mechanisms.

Friedrich Miescher

The scientist who discovered a phosphorus-rich acid termed nuclein (later nucleic acid) in the nuclei of salmon sperm in $1868$.

Oswald Avery

The scientist who demonstrated that bacterial transformation uses DNA rather than protein.

Nucleoside

A structural unit consisting of a nitrogenous base and a pentose sugar linked via an N-glycosidic bond.

Nucleotide

A chemical unit consisting of a nucleoside and one or more phosphate groups esterified to the hydroxyl on carbon $5$ of the sugar.

Purines

Double-ring nitrogenous bases including Adenine (A) and Guanine (G).

Pyrimidines

Single-ring nitrogenous bases including Cytosine (C) and Thymine (T).

Antiparallel

A structural orientation where the $5'$ end of one DNA strand is paired with the $3'$ end of a second strand.

Phosphodiester Bond

The $3'$ to $5'$ linkage that connects deoxyribonucleotides together in the primary structure of DNA.

Topoisomerase I

An enzyme that cleaves just one strand of the DNA backbone to allow rotation and change topologic conformation.

Topoisomerase II

An enzyme that cleaves both strands of the DNA backbone to change topologic conformation, utilizing ATP as an energy source.

Camptothecin

An antitumor drug that specifically inactivates Topoisomerase I.

Z-DNA

An alternative left-handed double helix structure characterized by a zigzag shape.

Nucleosome

A structural unit of eukaryotic DNA formed by DNA coiling twice around a histone octamer (composed of two each of H2A, H2B, H3, and H4).

$T_m$ (Melting Temperature)

The temperature at which complementary DNA strands dissociate; it varies by ionic condition and is higher in sequences rich in G-C pairs.

Pseudogenes

Copies of DNA that have accumulated many mistakes and are typically unusable, often arising from duplication or processed RNA intermediate.

SINES (Short Interspersed Nuclear Elements)

Repetitive DNA elements, such as Alu repeats, that are approximately $280$ letters long and make up $10\%$ of the human genome.

LINES (Long Interspersed Nuclear Elements)

Repetitive DNA elements, such as the L1 family, that are more than $500$ letters long, make up $20\%$ of the genome, and encode a reverse transcriptase.

Minisatellites (VNTR)

Short DNA sequences ($14$ to $50$ letters) whose repeat numbers vary per person, enabling their use in genetic fingerprinting and paternity testing.

SNP (Single Nucleotide Polymorphism)

Common DNA differences occurring at single positions in more than $1\%$ of the population.

ORC (Origin Recognition Complex)

A group of six proteins that binds to the origin of replication to initiate DNA unwinding in eukaryotes.

Meier-Gorlin Syndrome

A rare genetic disorder caused by mutations in the Orc complex, characterized by small ears, absent/small kneecaps, and short stature.

MCM Complex

The replicative DNA helicase in eukaryotes that uses energy from ATP hydrolysis to break hydrogen bonds and unwind the double helix.

RPA (Replication Protein A)

The human single-stranded binding protein (SSB) required to stabilize single-stranded DNA once the helix is unwound.

DNA Polymerase $\alpha$-primase

The enzyme responsible for initiating DNA synthesis by making RNA primers.

PCNA (Proliferating Cell Nuclear Antigen)

A DNA clamp that facilitates polymerase binding to the DNA strand, loaded via the clamp loader RF-C.

DNA Polymerase $\gamma$

The specific DNA polymerase responsible for mitochondrial DNA synthesis.

AZT (Zidovudine)

A nucleotide analogue used in HIV treatment that inhibits replication by lacking a $3'$ hydroxyl group, leading to chain termination.

p53

A critical tumor suppressor protein that monitors DNA for damage at the G1/S cell cycle checkpoint.

Xeroderma Pigmentosum

A condition caused by defective excision repair (specifically the nuclease that cleaves DNA near pyrimidine dimers), resulting in extreme risk for skin lesions and cancer.

AP Site

An apurinic or apyrimidinic site created in DNA when uracil-DNA glycosidase removes a mutated or deaminated base.