DNA Structure, Function, and Gene Expression

Comprehensive vocabulary based on lecture notes covering DNA history, structure, replication, transcription, translation, and mutations.

DNA (Deoxyribonucleic Acid)

The blueprint for life; the molecule that encodes the genetic instructions used in the development and functioning of all known living organisms and viruses.

Gregor Mendel

Known as the father of genetics; a monk who played an important role in the discovery of genes and heredity through his experiments with peapods.

Johannes Miescher (1869)

The Swiss physician who first isolated DNA, which he called nuclein, and determined it is not a protein but is rich in nitrogen and phosphorus.

Phoebus Levene (1919)

Identified the base, sugar, and phosphate nucleotide unit and suggested DNA consisted of a string of nucleotide units linked by phosphate groups.

Albrecht Kossel (1878)

Isolated the non-protein component of nuclein, nucleic acid, and later isolated its five primary nucleobases.

Frederick Griffith (1928)

Discovered a breakthrough in heredity while trying to find a vaccine against Streptococcus pneumoniae by injecting bacterial strands into mice.

William Astbury (1937)

Produced the first X-ray diffraction patterns that showed DNA had a regular structure.

Avery-MacLeod-McCarty experiment (1944)

Demonstrated that isolated DNA was the material of which genes and chromosomes are made.

Erwin Chargaff (1950)

Discovered two rules regarding base pair makeup that helped lead to the discovery of the double helix structure.

Rosalind Franklin

A British biophysicist and X-ray crystallographer whose X-ray diffraction images of DNA fibers provided key data for understanding its structure.

Watson-Crick Model (1953)

A molecular model describing DNA as a double-stranded helix where two phosphate-sugar chains are held together by pairs of bases.

Nucleotide

The monomer of nucleic acids, consisting of a five-carbon sugar, a phosphate group, and a nitrogenous base.

Pyrimidines

A category of nitrogenous bases that includes Thymine ($T$) and Cytosine ($C$).

Purines

A category of nitrogenous bases that includes Adenine ($A$) and Guanine ($G$).

Phosphodiester bond

The chemical bond formed during a condensation reaction that links the $3'$ carbon of one sugar to the phosphate on the next nucleotide's $5'$ carbon.

Antiparallel

The arrangement of DNA strands where the sequences of atoms in the two chains run in opposite directions.

DNA Replication

The process occurring in the nucleus in preparation for cell division where parental DNA strands separate and complementary bases are added to template strands.

Semi-conservative model

A model of replication where each resulting double helix contains one new strand and one old (parental) strand.

DNA Helicase

The enzyme responsible for unwinding and separating the two strands of parental DNA during replication.

DNA Polymerase

The enzyme that adds nucleotides only to the $3'$ end of a growing strand and provides a proofreading function.

Okazaki fragments

Short segments of DNA constructed on the lagging strand that are later joined by DNA ligase.

DNA Ligase

An enzyme that joins Okazaki fragments or other segments of DNA together where they meet.

Central Dogma

The molecular chain of command in eukaryotes where information flows from DNA in the nucleus to RNA, and then to protein synthesis in the cytoplasm.

Transcription

The process by which RNA is assembled in the nucleus using one strand of DNA as a template.

Promoter

A specific DNA sequence where RNA polymerase attaches to begin transcription.

Messenger RNA ($mRNA$)

The type of RNA that contains the protein-building message and specifies the order of the amino acid sequence.

Ribosomal RNA ($rRNA$)

The type of RNA that serves as a component of ribosomes along with proteins.

Transfer RNA ($tRNA$)

The type of RNA that delivers specific amino acids to a ribosome during protein synthesis.

Introns

Non-coding sections of an RNA transcript that are removed during post-transcriptional modification.

Exons

The coding regions of an RNA transcript that are spliced together to form the final $mRNA$.

Codon

A sequence of three RNA bases in a row that codes for one specific amino acid.

Genetic Code

A universal set of rules relating 64 possible codons to 20 amino acids; it includes one start codon (methionine) and three stop codons.

Anticodon

The three-nucleotide sequence on a $tRNA$ molecule that is complementary to an $mRNA$ codon.

Translation

The process where ribosomes interact with $tRNAs$ to translate $mRNA$ codons into a polypeptide chain.

Mutation

A permanent change in the DNA sequence, which can be spontaneous or caused by mutagens like $X-rays$ and $UV$ light.

Base-pair substitution

A type of mutation where a single base pair changes, which can be silent, nonsense, or missense.

Frameshift mutation

A mutation resulting from the deletion or insertion of one or more nucleotides, causing all subsequent codons to be misread.

Sickle Cell Anemia

A condition caused by a base-pair substitution in the beta globin gene, leading to crescent-shaped red blood cells.