25
Dec
2009
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Glossary

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C

C
(1) In DNA or RNA, cytosine. (2) In proteins, cysteine.
C-terminal
(see carboxy terminal)
C-value paradox
The apparent lack of correlation between the C value and the level of morphological complexity.
cap site (transcription initiation site)
In the DNA, the site where transcription starts. In the RNA, the site that is capped during the process of mRNA maturation.
capping
The modification of the 5' end of pre-mRNA in eukaryotes whereby a GTP is added to the molecule via a 5' to 5' triphosphate bond.
Captain Kidd
A famed pirate hunter of the 1600s; also a bar in Woods Hole, Massachusetts USA.
carboxy terminal (C-terminal)
The COOH end of a polypeptide.
carrying capacity
The maximum number of individuals of a given species that can be sustained in a defined habitat.
catalyst
A compound that lowers the energy necessary to activate a chemical reaction without being consumed or altered by it.
cDNA
(see complementary DNA)
chain
A Markov-chain.
chimeric protein
(see mosaic protein)
chromatid
(1) Each of the two copies produced by chromosome replication. (2) Each of the two DNA strands that comprise the chromosome.
chromosomal duplication
(see aneuploidy)
clade
(1) According to the rigorous definition, a taxon consisting of a single species and all its descendants representing a monophyletic branch on an evolutionary tree. (2) In looser usage, as above, except that some descendants are not represented. (3) In reference to extant organisms, a subgroup of organisms from among a larger group under consideration sharing a common ancestor not shared by the other organisms in the group.
cladogenesis
(see speciation)
classification
(see taxonomy)
coalescence
Uniting of lineages in the past.
codominance (genic selection)
The equal contribution to fitness made by the two alleles at a locus in a diploid organism.
codon
A triplet of adjacent nucleotides in mRNA that either codes for an amino acid carried by a specific tRNA or specifies the termination of the translation process.
codon family
All the codons that code for the same amino acid and differ from each other only at the third position (e.g., among the six codons for leucine, UUA and UUG form one family, and CUU, CUC, CUA and CUG form another).
codon usage
The frequency with which members of a codon family are used in protein-coding genes.
coenzyme
An organic nonprotein molecule that does not bind the enzyme but is required for the function of the enzyme by acting as an intermediate carrier of electrons, atoms, or groups of atoms.
cofactor
An inorganic molecule required by an enzyme in order to function.
coincidental evolution
(see concerted evolution)
colinearity
The exact correspondence between the DNA sequence of intronless genes and the amino acid sequence of the encoded protein.
complementarity
The antiparallel pairing of nucleotides in double-stranded DNA, double-stranded RNA, or DNA-RNA duplexes.
complementary DNA (cDNA)
DNA synthesized from an RNA template by the enzyme reverse transcriptase.
complex (composite) transposon
A transposon flanked by two complete, independently transposable insertion sequences.
compositional assimilation
The accumulation of point mutations in a pseudogene that eventually obliterates its sequence similarity to the functional gene from which it has been derived and makes its nucleotide composition similar to neighboring DNA sequences.
concerted evolution (horizontal evolution, coincidental evolution)
Maintenance of homogeneity of nucleotide sequences among members of a gene family in a species, although the nucleotide sequences change over time.
conditional fixation time
The time until fixation of a mutant allele that will eventually become fixed in the population.
consensus sequence
A sequence that represents the most prevalent nucleotide or amino acid at each site in a number of homologous sequences.
conservative substitution
The substitution of an amino acid by another with similar chemical properties.
constant site or constant region
A site or region within the DNA that is occupied by the same nucleotide in all homologous sequences under comparison.
convergence
The independent evolution of similar genetic or phenotypic traits.
convergent substitution
The substitution of two different nucleotides by the same nucleotide at the same nucleotide site in two homologous sequences.
corrected AIC
(see AICc)
crossing-over
The process of exchange of genetic material between two homologous chromosomes leading to recombination of linked genes. Presumed to occur through breakage of both chromosomes at homologous sites followed by reunion after exchange.
cyanobacteria
A type of photosynthetic eubacteria possessing the ability to photosynthesize. Formerly called blue-green algae.