Molecular Structure of DNA and RNA

Vocabulary review flashcards covering key historical experiments on genetic material (Griffith, Avery-MacLeod-McCarty, Hershey-Chase) and the molecular structure of DNA, RNA, and nucleotides.

Four Criteria of Genetic Material

The key requirements that the genetic material of life must fulfill: contain information to determine traits, transmit from parent to offspring, replicate faithfully, and exhibit variation to account for phenotypic differences.

Type S (Smooth) Strain

A virulent strain of Streptococcus pneumoniae that secretes a polysaccharide capsule protecting it from the host immune system, forming smooth colonies on solid media.

Type R (Rough) Strain

A nonvirulent strain of Streptococcus pneumoniae that is unable to secrete a polysaccharide capsule and forms colonies with a rough appearance.

Griffith's Transformation Experiment

A 1928 experiment demonstrating that living nonvirulent Type R bacteria could be transformed into virulent Type S bacteria when coinjected into mice with heat-killed Type S bacteria.

DNase

An enzyme that selectively breaks down DNA; its addition prevented the transformation of Type R bacteria into Type S in Avery, MacLeod, and McCarty's experiments.

RNase

An enzyme that selectively breaks down RNA, which did not inhibit the transformation of Type R cells into Type S cells.

Protease

An enzyme that breaks down proteins, which failed to prevent the transformation of Type R cells into Type S cells in Avery, MacLeod, and McCarty's experiments.

T2 Bacteriophage

A virus that infects Escherichia coli cells, consisting of a DNA core enclosed within a protein capsid head, sheath, base plate, and tail fibers.

$^{32}\text{P}$ Labeling

A radioactive phosphorus isotope used by Hershey and Chase to selectively label bacteriophage DNA, showing that most ($65\%$) remained associated with the host cells in the pellet after blending.

$^{35}\text{S}$ Labeling

A radioactive sulfur isotope used by Hershey and Chase to selectively label bacteriophage proteins, showing that $80\%$ was sheared off into the supernatant after blending.

Friedrich Miescher

The scientist who first isolated nucleic acids in 1869 as a phosphorus-containing substance from the nuclei of white blood cells collected from discarded surgical bandages.

Levels of Nucleic Acid Structure

The structural hierarchy of nucleic acids consisting of nucleotides, linear single strands, the double helix, and complex three-dimensional structures.

Nucleotide

The fundamental repeating monomeric unit of nucleic acids, consisting of a pentose sugar, a phosphate group, and a nitrogenous base.

Purines

Double-ring nitrogenous bases found in nucleic acids, specifically adenine (A) and guanine (G).

Pyrimidines

Single-ring nitrogenous bases found in nucleic acids, including thymine (T), uracil (U), and cytosine (C).

D-Deoxyribose

The five-carbon pentose sugar found in DNA nucleotides, characterized by having a hydrogen atom ($-\text{H}$) rather than a hydroxyl group attached to the $2'$ carbon.

D-Ribose

The five-carbon pentose sugar present in RNA nucleotides, characterized by a hydroxyl group ($-\text{OH}$) attached to the $2'$ carbon position.

Nucleoside

A molecule consisting of a purine or pyrimidine base covalently linked to a pentose sugar (such as adenosine), without attached phosphate groups.