Nucleic Acids, Gene Expression, and Cell Division

Comprehensive vocabulary flashcards covering basic nucleic acid structure, historical DNA experiments, replication mechanisms, gene expression (transcription and translation), mutations, and the cell cycle as described in the lecture notes.

Purines

Larger nitrogenous bases with a double-ring structure consisting of two fused rings; examples include Adenine and Guanine.

Pyrimidines

Smaller nitrogenous bases with a single ring structure; examples include Cytosine, Thymine (found only in DNA), and Uracil (found only in RNA).

Nucleotide

The building block of a nucleic acid polymer, composed of a pentose sugar, a nitrogenous base, and a phosphate group.

Phosphodiester bond

The covalent bond that links nucleotides together to form the sugar-phosphate backbone of a DNA or RNA strand.

Chargaff's Rule

A rule established by Erwin Chargaff in $1950$ stating that DNA base composition differs between species and that the amounts of $A=T$ and $G=C$ must total $$100\%$.

Glycosidic Bond

A covalent bond formed via condensation between the $-OH$ group on carbon $1'$ of a sugar and the Hydrogen of a nitrogenous base.

Transforming Principle

The discovery by Frederick Griffith in $1928$ that something from dead S-strain bacteria transformed live R-strain bacteria into virulent S-type bacteria.

Hershey & Chase Experiment

A study in $1952$ using bacteriophages labelled with Radio-isotopes $S-35$ and $P-32$ which proved that DNA, not protein, is the genetic material.

Meselson & Stahl Experiment

A $1958$ experiment using heavy nitrogen $N^{15}$ and light nitrogen $N^{14}$ that proved DNA replicates according to the semiconservative model.

Helicase

An enzyme that unzips DNA by breaking the hydrogen bonds between strands, creating replication forks for bidirectional replication.

Topoisomerase

An enzyme that relieves the tension generated by the unwinding of the DNA double helix during replication.

DNA Polymerase III

The enzyme responsible for building new DNA strands by synthesizing DNA in the $5'-3'$ direction.

DNA Polymerase I

The enzyme that removes RNA primers and replaces them with DNA nucleotides.

Okazaki Fragments

Short fragments of DNA synthesized on the lagging strand during DNA replication.

Telomeres

Non-coding DNA sequences at the end of linear chromosomes that act as a 'buffer zone' to protect genetic information from damage.

Central Dogma

The conceptual framework explaining how genetic information flows from DNA to RNA and then to Protein.

Promoter

A specific DNA sequence that specifies where transcription starts and serves as the binding site for RNA polymerase.

Euchromatin

Loosely packed chromatin in the nucleus where genes are typically active and expressed.

Heterochromatin

Tightly packed chromatin where genes are usually not expressed.

Nucleosome

A structural unit consisting of DNA coiled around a group of $8$ positively charged histone proteins.

Introns

Non-coding regions of pre-mRNA that are removed by spliceosomes during RNA processing.

P site (Peptidyl-tRNA binding site)

The ribosomal binding site that holds the tRNA carrying the growing polypeptide chain.

Wobbling

The flexible pairing observed at the third base of a codon, allowing a single tRNA to recognize more than one codon.

Nonsense mutation

A type of substitution mutation where a codon is changed into a stop codon, terminating protein synthesis prematurely.

Karyotype

An ordered display of the $23$ pairs of human chromosomes, grouped according to size and length.

S phase

The specific part of interphase in the cell cycle dedicated to DNA replication, resulting in $92$ chromatids.

Anaphase

The stage of mitosis where sister chromatids separate into individual chromosomes and move toward opposite poles.