molecular biology

nucleic acids

DNA and RNA are examples; so called because they are found in the nucleus and possess many acidic phosphate groups.

adenine

one of the four aromatic bases found in DNA and RNA; a purine that pairs with thymine (in DNA) and uracil (in RNA).

guanine

one of four aromatic bases found in DNA and RNA; a purine that pairs with cytosine.

cytosine

one of four aromatic bases found in DNA and RNA; a pyrimidine that pairs with guanine.

thymine

one of four aromatic bases found in DNA and RNA; a pyrimidine that pairs with adenine.

genome

all the genetic information in an organism; all of an organisms chromosomes.

chromosome

a single piece of double-stranded DNA; part of the genome of an organism.

DNA gyrase

a prokaryotic enzyme used to twist the single circular chromosome of prokaryotes upon itself to form supercoils.

histones

globular proteins that assist in DNA packaging in eukaryotes. histones form octamers around which DNA is wound to form a nucleosome.

nucleosome

a structure composed of two coils of DNA wrapped around an octet of histone proteins.

nucleoside

a structure composed of a ribose molecule linked to one of the aromatic bases.

chromatin

DNA that is densely packed around histone proteins.

transcription

the enzymatic process of reading a strand of DNA to produce a complementary strand of RNA.

DNA

a long linear polymer found in the nucleus of a cell and formed from nucleotides and shaped like a double helix

RNA

a long linear polymer of nucleotides found in the nucleus but mainly in the cytoplasm of a cell where it is associated with microsomes

translation

the process of reading a strand of mRNA to synthesize protein. protein translation takes place on a ribosome.

mRNA

messenger RNA; the type of RNA that is read by a ribosome to synthesize protein.

ribosome

a structure made of two protein subunits and rRNA; this is the site of protein synthesis in a cell.

rRNA

ribosomal RNA; the type of RNA that associates with ribosomal proteins to make a functional ribosome.

genetic code

the "language of molecular biology that specifies which amino acid corresponds to which three-nucleotide group.

codon

a group of 3 nucleotides that is specific for a particular amino acid, or that specifies "stop translating".

point mutation

a type of mutation in DNA where a single base is substituted for another.

insertion mutation

a mutation in which one or more extra nucleotides are added into the DNA sequence.

deletion mutation

a mutation in which a nucleotide is removed from the DNA sequence.

frameshift mutation

a mutation caused by the insertion or deletion of base pairs in a gene sequence in DNA such that the reading frame of the gene is altered.

replication

the duplication of DNA

DNA pol

DNA polymerase; an enzyme that replicates DNA. eukaryotes have one version, prokaryotes have three.

primase

an RNA polymerase that creates a primer to initiate DNA replication. DNA pol binds to the primer and elongates it.

helicase

an enzyme that unwinds the double helix of DNA and separates the DNA strands in preparation for DNA replication.

origin of replication

the specific location on an DNA strand where replication begins.

uracil

one of four aromatic bases found in RNA; a pyrimidine that pairs with adenine.

tRNA

transfer RNA; the type of RNA that carries an amino acid from the cytoplasm to the ribosome for incorporation into a growing protein.

hnRNA

heterogenous nuclear RNA; the primary transcript made in eukaryotes before splicing.

splicing

one time of eukaryotic mRNA processing in which introns are removed from the primary transcript and exons are ligated together.

intron

a nucleotide sequence that intervenes between protein-coding sequences.

exons

a nucleotide sequence in RNA that contains protein-coding information; typically separated by introns.

5' cap

a methylated guanine nucleotide added to the 5' end of eukaryotic mRNA. necessary to initiate translation of the mRNA.

anticodon

a sequence of three nucleotides that is complementary to a specific codon in mRNA.

70S ribosome

the prokaryotic ribosome

80S ribosome

the eukaryotic ribosome

P site

petidyl-tRNA site; the site on a ribosome where the growing peptide is found during translation.

peptidyl transferase

the enzymatic activity of the ribosome that catalyzes the formation of a peptide bond between amino acids.