Genes: The Messages of Life - DNA and RNA Biochemistry

Practice flashcards covering DNA and RNA structure, cell cycle phases, DNA replication, and transcription based on biochemistry lecture notes.

Biochemical systems in dynamic equilibrium

A state where biomolecules or complexes fluctuate between different states but the population distribution remains approximately constant.

$G_1$ (Gap $1$)

The phase of interphase where organelles and cytoplasmic components are copied.

$S$ (Synthesis)

The phase of the cell cycle during which DNA is replicated.

$G_2$ (Gap $2$)

The phase where enzymes required for cell division are produced.

Prophase

Phase where chromosomes condense, the cytoskeleton disassembles, centrioles migrate to poles, and the nuclear envelope breaks down.

Metaphase

The phase of cell division where chromosomes align at the equator of the cell.

Anaphase

The phase where chromosomes separate and move to opposite poles.

Telophase

Phase where chromosomes condense, the nuclear envelope re-forms, and daughter cells separate via cell membrane or wall synthesis.

Nucleotide

A monomeric unit of DNA consisting of a deoxyribose sugar, a phosphate group, and a nitrogen-rich organic base.

Phosphodiester bonds

Covalent sugar-phosphate linkages between the $5'$ and $3'$ positions of adjacent ribose units in a DNA strand.

Antiparallel

The arrangement of two DNA strands aligned in opposite directions, such as one proceeding $5'$ to $3'$ and the other $3'$ to $5'$.

$dG$, $dC$, $dA$, $dT$

Abbreviated nomenclature for DNA nucleotides, where 'd' indicates deoxyribose and the capital letter represents the base.

Nucleoside

A molecule consisting of a nitrogenous base and a sugar but lacking a phosphate group.

Purines

DNA bases ($A$ and $G$) composed of fused $6$-membered and $5$-membered rings.

Pyrimidines

DNA bases ($T$ and $C$) consisting of a single $6$-membered ring.

Watson-Crick base pairs

Specific pairings where $A$ forms hydrogen bonds with $T$ and $G$ forms hydrogen bonds with $C$.

Hydrogen donor

A group consisting of a hydrogen atom covalently bonded to an electronegative atom (usually $O$ or $N$), such as an $OH$ or $NH$ group.

Hydrogen acceptor

An electronegative atom (usually $O$ or $N$) that has non-bonded pairs of electrons.

$G:C$ base pair stability

A $G:C$ base pair has $3$ hydrogen bonds, making it more stable and requiring more energy to break than an $A:T$ base pair which has $2$.

DNA Double Helix structure

A twisted conformation where consecutive base pairs are stacked with a $36^\text{o}$ twist, resulting in $10$ base pairs per turn.

DNA Polymerase

The enzyme that synthesises a new DNA strand using a template strand, a primer, and $dNTPs$.

Leading strand

The strand of DNA that is synthesised continuously in the $5'$ to $3'$ direction.

Lagging strand

The strand of DNA synthesised in segments called Okazaki fragments.

Topoisomerase

An enzyme that breaks and reforms DNA strands to prevent knots during unwinding and rewinding.

Ciprofloxacin

A broad-spectrum quinolone antibiotic that inhibits bacterial topoisomerase, causing bacterial DNA destruction.

Ribose

The sugar found in RNA, which has a hydroxyl ($OH$) group at the $2'$ position instead of a hydrogen atom.

Uridine monophosphate ($U$)

The RNA nucleotide that replaces deoxythymidine monophosphate ($dT$); it lacks a methyl ($CH_3$) group but pairs with $A$.

Primary structure (RNA)

The linear sequence of nucleotides in an RNA chain.

Secondary structure (RNA)

The formation of local 'hairpins' where sections of the RNA chain form a duplex with each other.

Tertiary structure (RNA)

The $3D$ conformation formed when different regions of the RNA pack against each other.

RNA Polymerase

The enzyme responsible for RNA synthesis using a DNA template and $NTPs$, requiring no primer.

Promoter

A specific DNA sequence on the non-coding (template) strand where RNA polymerase binds to define the start of transcription.

Coding (non-template) strand

The DNA strand whose sequence is identical to the resulting RNA transcript, except each $T$ is replaced by $U$.

Non-coding (template) strand

The DNA strand used by RNA polymerase to create a complementary RNA sequence.