25
Dec
2009
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Glossary

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M

M
Methionine.
match
In sequence alignment, the existence of the same base in a homologous position in both sequences.
maturation
The formation of mRNA from pre-mRNA.
maximum likelihood
A statistical method of estimation.
maximum parsimony (parsimony)
The selection of the phylogenetic tree requiring the least number of substitutions from among all possible phylogenetic trees as the most likely to be the true phylogenetic tree.
MCMC
Markov-chain Monte Carlo.
MCMCMC
Metropolis-coupled Markov-chain Monte Carlo.
meiosis (reduction division)
The eukaryotic cell division process used in producing haploid gametes from diploid cells. Meiosis is characterized by a reduction division which ensures that each gamete contains one representative of each pair of autosomes and half the sex chromosomes.
meiotic drive
Any process which causes some alleles to be over-represented in the gametes which are formed during meiosis.
Mendel's second law
(see independent assortment)
Mendelian segregation (Mendel's first law, segregation)
The Mendelian principle that the two different alleles of a gene pair in a heterozygote separate from each other during meiosis to produce two kinds of gametes in equal ratios, each bearing a different allele.
middle-repetitive DNA
The fraction of genomic DNA consisting of relatively long sequences repeated on the average from tens to hundreds of times.
migration
In population genetics, the movement of individuals or genes among populations.
mismatch
In sequence alignment, the existence of different bases in a homologous position in the two sequences.
mitosis
The mode of eukaryotic cell division that produces two daughter cells possessing the same chromosomal complement as the parent cell.
mobile element
(see transposable element)
module (structural domain)
In globular proteins, a structurally independent, stable, and compact spatial unit that can be distinguished from all other parts. Usually, consisting of a contiguous stretch of amino acids.
molecular clock
(1) The rate at which mutations accumulate in a given genomic segment. (2) The hypothesis that, in any given gene or DNA sequence, mutations accumulate at an approximately constant rate in all evolutionary lineages as long as the gene or the DNA sequence retains its original function. The extent to which the clock applies to all genes and all organisms is controversial.
monomorphic
A population in which virtually all individuals have the same allele at a locus.
monophyletic
Sharing a common ancestor.
mortality
A fitness component. The average probability of an individual of a given genotype to die before reaching a certain age (e.g., mortality to mean reproductive age).
mosaic protein (chimeric protein)
A protein encoded by a gene that contains regions from different genes. Also, an artificial protein derived through genetic engineering.
mRNA (messenger RNA)
A molecule of RNA that serves as a template for protein synthesis.
multiple substitutions
The successive occurrence of two or more substitutions at the same nucleotide site in a DNA sequence.
mutagen
A physical or chemical entity that increases the mutation rate.
mutant
A new variant form of a gene.
mutation
The alteration of a DNA sequence to produce a different form than the original.
mutation rate
The number of mutations arising in an individual per nucleotide site or per gene per unit time.
mutational bias
A pattern of mutation in which the four nucleotides show different propensities to mutate or in which mutations result in a certain nucleotide more often than others. Often results in the uneven accumulation of certain nucleotides.