M Methionine in proteins M13 A single stranded DNA bacteriophage (bacteria virus) M13 template A piece of DNA that has been cloned into the M13 vector
and can be used for sequencing. machine language the set of commands that the microprocessor uses to carry
out functions. macrochromosome One of the larger, gene-deficient chromosomes seen in the
nuclei of chickens and various other species MADS box A DNA-binding domain found in several transcription
factors involved in plant development main diagonal in an intersequence dot matrix comparison, the main
diagonal is a diagonal or diagonals that predominate over
the others. The main diagonal is often inferred to represent
the homologous matching of the two sequences. maintenance methylation Addition of methyl groups to positions on newly
synthesized DNA strands that correspond with the positions
of methylation on the parent strand. major groove the larger of the two grooves that spiral around the
surface of teh B-form of DNA major histocompatibility complex A mammalian multigene family coding for cell surface
proteins and including several multiallelic genes map A chart showing the positions of genetic and/or physical
markers in a genome. These markers can be restriction sites
or other patterns. MAP kinase A signal transduction pathway mapping reagent A collection of DNA fragments spanning a chromosome or
the entire genome and used in STS mapping. marker An identifiable physical location on a nchromosome (e.g.,
restriction enzyme cutting site, gene, STS) whose
inheritance can be monitored. Also a gene, carried by a
cloning vector, that codes for a distinctive protein product
and/or phenotype and so can be used to determine if a cell
contains a copy of the cloning vector. Commonly used markers
are antibiotic resistance genes, beta-galactosidase, or
Green Fluorescent Protein. Markov model A statistical model for sequences in which the
probability of each letter depends on the letters that
precede it. masking Some regions of sequences have particular
characteristics, such as repeated patterns, that lead to
spurious high scores. Masking replaces these regions of
sequence with an "X" for proteins or "N" for nucleic acids.
See filtering. match In sequence alignment, the existence of the same base in
a homologous position in both sequences. Maternal-effect gene A Drosophila gene that is expressed in the parent and
whose mRNA is subsequently injected into the egg, after
which it influences development of the embryo. Mating type The equivalent of male and female for a eukaryotic
microorganism Mating type switching The ability of yeast cells to change mating typoe by gene
conversion Marix-associated region (MAR) An AT-rich segment of a eukaryotic genome that acts as an
attachment point to the nuclear matrix. Maturase A protein, coded by a gene in an intron, thought to be
involved in splicing. maturation The formation of mRNA from pre-mRNA Maximum Parsimony method A method for construction of phylogenetic trees requiring
the least number of substitutions from among all possible
phylogenetic trees. Mb megabase. One million base pairs of DNA MDM Mutation Data Matrix, 1978. The most common scoring
system for proteins. MDM is the log-odds form of the PAM-250
mutation probability matrix. mediator A protein complex that forms a contact between various
transcription factors and the C-terminal domain of the
largest subunit of the yeast RNA polymerase II. meiosis 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 melting Denaturatino of duplexes into single-stranded nucleic
acids melting temperature Tm The temperature at which the two strands of
a double-stranded nucleic acid molecule or base-paired
hybrid detach due to complete breakage of hydrogen
bonding. Mendelian segregation Mendel's first law. The 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. metric distance A scoring system that has the following properties: The scoring system as a whole obeys the triangle
inequality. messenger RNA (mRNA) the transcript of a protein-coding gene. metadata Information about the structure of the data in a
database. If a database is relational, the metadata contains
the names of the relations, the attributes of those
relations and the data types for those attributes. metaphase chromosome A chromosome at the metaphase stage of cell division,
when the chromatin takes on its most condensed structure and
features such as the banding pattern can be visualized. microarray a low-density array of DNA molecules used for parallel
hybridization analysis microsatellite A type of simple sequence length polymorphism comprising
tamdem copies of, usually, di-, tri- or tetranucleotide
repeat units. Also called a simple tandem repeat (STR). migration In population genetics, the movement of individuals or
genes among populations. minichromosome one of the smaller, gene-rich chromosomes seen in the
nucleus of chickens and various other species minigene the name given to the pair of exons carried by a cloning
vector used in the exon-trapping procedure. minimal medium A medium that provides only the minimum nutritional
requirements for growth of a microorganism. minisatellite A type of simple sequence length polymorphism comprising
tandem copeies of repeats that are a few tens of nucleotides
in length. Also called a variable number of tandem repeats
(VNTR). Mismatch in sequence alignment, the existence of different bases
in a homologous position in the two sequences. missense mutation a codon that alters a codon to that for another amino
acid mitochondrion A DNA-containing organelle in eukaryotic cells that uses
an oxygen-requiring elecroin-transport system to transfer
chemical energy derived from the breakdown of food molecules
to ATP. mitochondrial genome The genome present in the mitochondria of a eukaryotic
cell mitosis the mode of eukaryotic cell division that produces two
daughter cells possessing the same chromosomal complement as
the parent cell mobile element transposable element model organism an organism which is relatively easy to study and hense
can be used to obtain informatino that is relevant to the
biology of a second organism that is more difficult to
study. modification assay A range of techniques used for locating bound proteins on
DNA molecules (e.g.,fingerprinting) modification interference A technique used to identify nucleotides involved in
interactions with a DNA-binding protein moderately repetitive genes Genes with a moderate number of copies in the haploid
genome 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
continuous stretch of amino acids. molecular chaperone A protein that helps other proteins to fold. molecular clock The hypothesis that nucleotide or amino acid
substitutionns occur at more or less constant rate over
evolutionary time, like the slow ticking of a clock. It has
been proposed that given a calibration date, and a constant
molecular clock, the amount of sequence divergence can be
used to calculate the time that has elapsed since two
molecules diverged. molecular combing A technique for preparing restricted DNA molecules for
optical mapping molecular evolution The gradual changes that occur in genomes over time due
to the accumulation of mutations and structural
rearrangements resulting from recombination and
transposition molecular phylogenetics A set of techniques that enable the evolutionary
relationships between DNA sequences to be inferred by making
comparisions between those sequences. monohybrid cross A sexual cross in which the inheritance of one pair of
alleles is followed monomorphic a population in which virutally all individuals have the
same allele at a locus monophyletic Sharing a common ancestor Monte Carlo simulation A method of calculating significance where the analysis
in question is repeated using randomized or permuted
sequences, in order to determine the expected scores for
unrelated (random) sequences. mortality A fitness component. The average probability of an
individual of a given genotype to die before reaching a
certain 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 MPEG A method of encoding video that takes advantage of the
fact that one frame of a motion picture is very similar to
the frame before it. Thus, regions of one frame can be
represented by a pointer to a similar rregion in the
previous frame. M phase The stage of the cell cycle when mitosis or meiosis
occurs multicopy A gene, cloning vector, or other genetic element that is
present in multiple copies in a single cell. multifurcation A graphic representation of an unknown branching order in
a phylogenetic tree involving three or more taxa. multicysteine zinc finger A type of zinc finger DNA-binding domain in proteins. multigene family A set of genes derived by duplication of an ancestral
gene that display more than 50% similarity among them.
Frequently, in close linkage with each other, and possessing
similar or overlapping functions. multiple alignment An alignment of three or more sequences multiple alleles the different forms of a gene that has more than two
alleles 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. mutagenesis Treatment of a group of cells or organisms with a mutagen
as a means of inducing mutations. multiplexing A sequencing approach that uses several pooled samples
simultaneously, greatly increasing sequencing speed. multipoint cross A genetic cross in which the inheritance of three or more
markers is followed multiregional evolution A hypothesis that holds that modern humans in the Old
World are descended from Homo erectus populations
that left Africa over one million years ago. mutant A new variant form of a gene mutation the alteration of a DNA sequence to produce a different
form than the original. Any heritable change in DNA. compare
with polymorphism. mutation scanning A set of techniques for detection of mutations in DNA
molecules mutation screening A set of techniques for determining if a DNA molecule
contains a specific mutation 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 mutato or in which mutations
result in a certain nucleotide more often than others. Often
results in the uneven accumulation of certain
nucleotides.
