25
Dec
2009
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Glossary

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G

G
(1) In DNA or RNA, guanine. (2) In proteins, glycine.
gamete
A reproductive cell with a haploid number of chromosomes.
gap
An insertion or a deletion. In sequence alignment, a pair containing a null base.
gap penalty
The assessment of how frequent a gap event occurs in evolution in comparison with the frequency of occurrence of point substitutions. In alignment algorithms, either a factor multiplied by the total length of gaps or a function multiplied by the number of gaps of a given length, which is used to compare the likelihood of gaps and substitutions.
GARLI
Genetic Algorithm for Rapid Likelihood Inference; a program for phylogenetic analysis using a genetic algorithm.
gene
A sequence of genomic DNA or RNA that is essential for a specific function.
gene conversion
A nonreciprocal recombination process resulting in a sequence becoming identical with another.
gene diversity
A measure of genetic variability in a population. The mean expected heterozygosity per locus in a population.
gene duplication
Generally, the production of two copies of a DNA sequence. Specifically, the duplication of an entire gene sequence.
gene family
A group of related genes of similar sequence and function resulting from multiple duplications and subsequent mutational variation among the different copies.
gene pool
All the genes in a sexually reproducing population.
gene sharing
The situation whereby a gene acquires and maintains a second function without duplication and without loss of its primary function.
gene substitution
The process whereby a new mutant allele reaches fixation in a population.
gene tree
A phylogenetic tree that has been constructed from one or multiple genes from each species.
generation time
The average time span between two successive generations. Sometimes defined as the mean age of the parents at which they give birth to their middle child.
genetic algorithm
An algorithm for combinatorial optimization problems inspired by genetics. Possible solutions are represented by individuals in one or more populations and operations on possible solutions (individuals) corresponding to genetic processes (e.g., mutation, recombination, selection, migration).
genetic code
A set of rules for the translation of codons into amino acids.
genetic distance (distance)
Broadly, any of several measures of the degree of genetic difference between individuals, populations, or species. In reference to molecular evolution, a measure of the number of nucleotide substitutions per nucleotide site between two homologous DNA sequences that have accumulated since the divergence between the sequences.
genetic drift
(see random genetic drift)
genic selection
(see codominance)
genome doubling
(see polyploidy)
genotype
The specific allelic constitution of an organism including alleles not expressed at the phenotypic level. Often, the allelic composition of one or few genes under investigation.
geometric mean
The nth root of the product of n terms.
germ-line cell
A sperm or egg cell, or one of their precursor cells.