DNA and its Role in Heredity

Comprehensive vocabulary flashcards covering DNA discovery, structure, replication, repair mechanisms, and PCR based on Chapter 13 lecture notes.

Transforming principle

A chemical substance from dead cells capable of producing a heritable change in another strain, first identified by Frederick Griffith.

Streptococcus pneumoniae

The species of bacteria used by Frederick Griffith to determine the existence of a transforming principle.

Oswald Avery

A scientist who demonstrated that DNA was the transforming principle by showing that activity was lost only when DNA was destroyed.

Hershey-Chase experiment

An experiment using bacteriophage T2 labeled with $^{35}S$ and $^{32}P$ which established conclusively that DNA, not protein, is the genetic material.

$$^{35}S$$

The radioactive isotope used by Hershey and Chase to label bacteriophage proteins.

$$^{32}P$$

The radioactive isotope used by Hershey and Chase to label bacteriophage DNA.

Transfection

The genetic transformation of eukaryotic cells.

Genetic marker

A gene that confers an observable phenotype, such as antibiotic resistance, used to identify transfected cells.

Transgenic organism

The result of transfecting a cell, such as an egg cell, with foreign DNA.

X-ray crystallography

A technique used by Rosalind Franklin to produce images of DNA which suggested a spiral or helical model.

Purines

Nitrogen-containing bases with a double-ring structure, specifically Adenine (A) and Guanine (G).

Pyrimidines

Nitrogen-containing bases with a single-ring structure, specifically Cytosine (C) and Thymine (T).

Chargaff’s rule

The observation that in DNA, the amount of $A = T$ and the amount of $C = G$, meaning the abundance of purines equals the abundance of pyrimidines.

Antiparallel

The arrangement in which the two polynucleotide chains of a DNA double helix run in opposite directions.

Major and minor grooves

Regions where the outer edges of nitrogenous bases are exposed on the DNA double helix.

Complementary base pairing

The specific pairing of Adenine with Thymine via two hydrogen bonds, and Cytosine with Guanine via three hydrogen bonds.

$5'$ end

The end of a DNA strand that terminates in a free phosphate group.

$3'$ end

The end of a DNA strand that terminates in a free hydroxyl group.

Semiconservative replication

The method of DNA replication where each parent strand serves as a template, resulting in two DNA molecules with one old and one new strand.

Origin of replication (ori)

A specific sequence on a chromosome where the replication complex binds and DNA replication begins.

Primer

A short starter strand, complementary to the DNA template, synthesized by primase to begin replication.

DNA polymerase

An enzyme that catalyzes the addition of nucleotides to the $3'$ end of a growing DNA strand.

DNA helicase

An enzyme that uses energy from ATP hydrolysis to unwind the DNA double helix.

Leading strand

The new DNA strand that is oriented to grow continuously at its $3'$ end as the replication fork opens.

Lagging strand

The new DNA strand synthesized in small, discontinuous stretches called Okazaki fragments.

Okazaki fragments

Small stretches of DNA synthesized on the lagging strand, each requiring its own primer.

DNA ligase

An enzyme that catalyzes the final phosphodiester linkage between Okazaki fragments.

Proofreading

An immediate repair mechanism where DNA polymerase and other proteins remove incorrectly paired nucleotides during replication.

Mismatch repair

A mechanism that detects and excises mismatched bases that were missed during the proofreading stage.

Excision repair

A repair mechanism that scans for and removes DNA damage caused by radiation or chemical reactions throughout the life of a cell.

Polymerase chain reaction (PCR)

A laboratory technique used to amplify specific DNA sequences using DNA polymerase and cyclic heating and cooling.

Thermus aquaticus

A hot springs bacterium from which heat-resistant DNA polymerase is obtained for use in PCR at temperatures near $90^{\circ}\text{C}$.