Genetics and DNA Replication Vocabulary

A comprehensive vocabulary review set created from lecture notes covering foundational genetics, historical DNA experiments, nucleic acid structures, DNA replication mechanisms, and characteristics of the genetic code.

Epigenesis

The process of development where an organism develops progressively from an egg to an adult.

Cell Theory

Theory proposed by Schleiden and Shwann in 1830 stating that all organisms are composed of cells and arise from pre-existing cells.

Alleles

Alternative forms or different versions of a gene (for example, eye color).

Mutations

A heritable change in a gene sequence that allows for variation in chemical composition.

Genotype

The specific set of alleles present for a given trait.

Chromosome Theory of Inheritance

Theory stating that inherited traits are controlled by genes residing on chromosomes, which are faithfully transmitted through gametes to maintain genetic continuity across generations.

Transforming Principle

The unknown substance identified in Griffith's experiment that transferred from heat-killed virulent $S$ strain Streptococcus pneumoniae to transform live non-virulent $R$ strain bacteria into virulent $S$ bacteria.

Avery, Macleod & McCarty Experiment

A 1944 experiment demonstrating that DNA, not protein or RNA, is the transforming material responsible for bacterial transformation and heredity by using selective enzymes (DNase, RNase, protease).

Hershey-Chase Experiment

A 1952 experiment using radioactive isotopes ${}^{32}P$ (DNA) and ${}^{35}S$ (protein) in bacteriophage T2 and E. coli, proving that DNA is the genetic material that enters the host cell to direct viral reproduction.

Reverse Transcriptase

An RNA-dependent DNA polymerase enzyme used by retroviruses to synthesize DNA from an RNA template.

Purines

Nine-membered double-ring nitrogenous bases comprising Guanine (G) and Adenine (A).

Pyrimidines

Six-membered single-ring nitrogenous bases comprising Cytosine (C), Uracil (U), and Thymine (T).

Nucleoside

A chemical unit consisting of a pentose sugar covalently bound to a nitrogenous base, lacking a phosphate group.

Nucleotide

The building block of nucleic acids consisting of a pentose sugar, a nitrogenous base, and a phosphate group.

Phosphodiester Bond

A covalent linkage connecting the $3'$ carbon of one deoxyribose sugar to the $5'$ carbon of the adjacent sugar via ester bonds on both sides of a phosphate group.

Chargaff Base Pairing

The principle stating that in double-stranded DNA, the amount of adenine equals thymine ($A = T$), the amount of guanine equals cytosine ($G = C$), and the sum of purines equals the sum of pyrimidines.

Hyperchromic Shift

A shift used to estimate base composition where higher $G-C$ content leads to a higher melting point ($T_m$) due to the presence of 3 hydrogen bonds compared to 2 in $A-T$ pairs.

Semiconservative Model

The model of DNA replication demonstrated by Meselson and Stahl (1958) showing that each newly replicated DNA molecule contains 1 original parental strand and 1 newly synthesized strand.

Leading Strand

The DNA strand that is synthesized continuously in the $5' \rightarrow 3'$ direction toward the replication fork.

Lagging Strand

The DNA strand that is synthesized discontinuously in the $5' \rightarrow 3'$ direction away from the replication fork as short Okazaki fragments.

Telomerase

A reverse transcriptase enzyme carrying its own RNA template that extends the $3'$ end of linear chromosomes, preserving terminal stability and protecting genes from degradation.

Degenerate Code

A characteristic of the genetic code meaning that a specific amino acid can be specified by more than one triplet codon.

Unambiguous Code

A characteristic of the genetic code meaning that each individual triplet codon specifies only one single amino acid.

Polynucleotide Phosphorylase

An enzyme used to catalyze the production of synthetic or artificial mRNA from ribonucleotide diphosphates (NDPs) without requiring a DNA template.

Wobble Hypothesis

The hypothesis stating that the first two ribonucleotides of a triplet codon are more critical for pairing, while the third position is less spatially constrained and does not strictly adhere to standard base-pairing rules.

Nonsense Mutation

A mutation that changes a codon to one of the three stop/termination codons ($UAG$, $UAA$, or $UGA$), leading to premature termination of translation.