Deoxyribonucleic Acid (DNA) Structure and Function

A comprehensive set of vocabulary flashcards covering DNA history, structure, replication, protein synthesis, and biotechnology applications based on the lecture notes.

Chromatin

The material that makes up eukaryotic chromosomes, which includes DNA.

Genes

Specific DNA sequences that carry genetic information transmitted from one generation to the next and direct cellular activities.

S-strain

A pathogenic or virulent form of Streptococcus pneumoniae that can be made non-pathogenic by heating.

R-strain

A non-pathogenic or avirulent form of Streptococcus pneumoniae.

Transforming Principle

The conceptual mechanism identified by Frederick Griffith where virulence-specifying information passed from dead S-strain cells into live R-strain cells.

Avery, MacLeod, and McCarty Experiment

A 1944 study that identified DNA as the genetic material by using enzymes like protease, RNase, and DNase to see which treatment destroyed the transforming ability of S-strain extracts.

Bacteriophages

Viruses that infect bacteria, composed only of DNA and protein, used in the Hershey and Chase experiment.

$\text{32P}$ and $\text{35S}$

Radioactive isotopes of phosphorus and sulfur used to label DNA and protein, respectively, in the Hershey and Chase experiment.

Nucleotide

The building block of DNA consisting of a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base.

Chargaff’s Rule

The finding that the amount of adenine equals thymine ($A = T$) and the amount of cytosine equals guanine ($C = G$).

Purines

The category of nitrogenous bases that includes adenine (A) and guanine (G).

Pyrimidines

The category of nitrogenous bases that includes cytosine (C) and thymine (T).

X-ray diffraction

The technique used by Rosalind Franklin and Maurice Wilkins to show DNA's helical structure and sugar-phosphate backbone.

Double Helix

The structure of DNA proposed by Watson and Crick in 1953, featuring antiparallel complementary strands.

Supercoiling

The formation of additional coils in DNA due to twisting forces, which helps pack DNA into a cell's nucleoid.

Topoisomerase I and II

Enzymes that control the process of DNA supercoiling in prokaryotes.

Plasmids

Small, circular, or linear DNA molecules in prokaryotes that often carry non-essential genes.

Regulatory sequences

DNA sections that determine when certain genes and associated cell functions are activated.

Histones

A family of proteins in eukaryotic cells that associate with DNA to assist in compaction.

Nucleosomes

Condensed structures formed when double-stranded DNA wraps around an octamer of histone proteins.

Telomeres

Specialized structures at the ends of eukaryotic chromosomes that protect them from nucleases and maintain integrity.

Semi-conservative model

The model of DNA replication confirmed by Meselson and Stahl where each new molecule consists of one parental strand and one daughter strand.

Replicon

A segment of DNA that is controlled by a single origin of replication.

Initiation

The first step of DNA replication where unwinding begins at an origin of replication and initiator proteins attach.

Helicase

The enzyme responsible for breaking hydrogen bonds connecting complementary base pairs during DNA unwinding.

Single-strand-binding proteins

Proteins that stabilize unwound DNA strands during replication initiation.

Replication Fork

The Y-shaped structure formed at each end of a replication bubble during DNA synthesis.

DNA polymerase III

The enzyme that facilitates the addition of new nucleotides to form a complementary strand in the $5′$ to $3′$ direction.

Leading Strand

The DNA strand synthesized continuously in the $5′$ to $3′$ direction from the parent strand.

Lagging Strand

The DNA strand formed in short segments away from the replication fork in a discontinuous manner.

Okazaki fragments

Short DNA fragments synthesized on the lagging strand during elongation.

Primase

The enzyme that synthesizes an RNA primer required for the initiation of a new DNA strand.

DNA polymerase I

The enzyme that removes RNA primers and fills the gaps with DNA fragments during replication.

DNA ligase

The enzyme that connects Okazaki fragments to form a continuous DNA strand.

Mutations

Permanent changes in the DNA sequence caused by errors such as base mispairing or strand slippage.

Mismatch repair

A process involving proteins that identify and fix deformities in newly synthesized DNA caused by mispaired bases.

Central Dogma of Genetics

The principle that genetic information flows unidirectionally and irreversibly from DNA to RNA to protein.

Transcription

The synthesis of RNA molecules using DNA strands as templates to transfer genetic information.

Promoter (TATA box)

The specific DNA sequence where transcription begins.

RNA polymerase

The enzyme that produces RNA by separating DNA strands and linking RNA nucleotides together.

Introns

Non-coding DNA sequences located between exons that are spliced out during RNA processing.

Exons

Expressed DNA sequences that code for amino acids and are joined together during RNA processing.

Spliceosomes

Molecular complexes that remove introns and join exons during the maturation of pre-RNA in the nucleus.

Translation Initialization

The stage bringing together mRNA, initiator tRNA with methionine, and ribosomal subunits at the start codon.

Translation Elongation

A three-step cycle where amino acids are added to a growing polypeptide chain with the help of elongation factors.

Release factor

A protein that binds to a stop codon at the A site, freeing the completed polypeptide and disassembling the translation complex.

DNA fingerprinting

A forensic application using simple tandem repeats (STRs) found in satellite DNA for identification.

Bioremediation

The use of genetically engineered organisms to clean oil spills and waste dumps.

Polymerase Chain Reaction (PCR)

A method invented in 1984 used to amplify specific DNA segments to produce billions of copies.