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Modern Genetic Analysis Glossary
I
Ig (immunoglobulin) See antibody.
Ile Isoleucine (an amino acid).
imago An adult insect.
immune system The animal cells and tissue that recognize and attack foreign substances within the body.
immunoglobulin See antibody.
immunohistochemistry The use of antibodies or antisera as histological tools for identifying patterns of protein distri-bution within a tissue or an organism. An antibody (or mixture of antibodies) that binds to a specific protein is tagged with an enzyme that can convert a substrate into a visible dye. The tagged antibody is incubated with the tissue, unbound antibody is washed off, and the enzymatic substrate is then added, revealing the pattern of protein (actually, antigen) localization.
in situ "In place"; see hybridization in situ.
in vitro In an experimental situation outside the organism (literally "in glass").
in vitro mutagenesis The production of either random or specific mutations in a piece of cloned DNA. Typically, the DNA will then be repackaged and introduced into a cell or an organism to assess the results of the mutagenesis.
in vivo In a living cell or organism.
inbreeding Mating between relatives.
inbreeding coefficient The probability of homozygosity that results because the zygote obtains copies of the same ancestral gene.
incomplete dominance The situation in which a heterozygote shows a phenotype quantitatively (but not exactly) intermediate between the corresponding homozygote phenotypes. (Exact intermediacy is no dominance).
independent assortment See Mendel's second law.
inducer An environmental agent that triggers transcription from an operon.
induction The relief of repression for a gene or set of genes under negative control.
inductive interaction The interaction between two groups of cells in which a signal passed from one group of cells causes the other group of cells to change their developmental state (or fate).
infectious transfer The rapid transmission of free episomes (plus any chromosomal genes that they may carry) from donor to recipient cells in a bacterial population.
inosine A rare base that is important at the wobble position of some tRNA anticodons.
insertion sequence (IS) A mobile piece of bacterial DNA (several hundred nucleotide pairs in length) that is capable of inactivating a gene into which it inserts.
insertional translocation The insertion of a segment from one chromosome into another nonhomologous one.
intercalating agent A chemical that can insert itself between the stacked bases at the center of the DNA double helix, possibly causing a frame-shift mutation.
interchromosomal recombination Recombination resulting from independent assortment.
interference A measure of the independence of crossovers from each other, calculated by subtracting the coefficient of coincidence from 1.
intermediate filaments A heterogeneous class of cytoskeletal elements characterized by an intermediate cable diameter, larger than that of microfilaments but smaller than microtubles.
interphase The cell cycle stage between nuclear divisions, when chromosomes are extended and functionally active.
interrupted mating A technique used to map bacterial genes by determining the sequence in which donor genes enter recipient cells.
interstitial region The chromosomal region between the centromere and the site of a rearrangement.
intervening sequence An intron; a segment of largely unknown function within a gene. This segment is initially transcribed, but the transcript is not found in the functional mRNA.
intrachromosomal recombination Recombination resulting from crossing-over between two gene pairs.
intron See intervening sequence.
inversion A chromosomal mutation consisting of the removal of a chromosome segment, its rotation through 180 degrees, and its reinsertion in the same location.
inverted repeat (IR) sequence A sequence found in identical (but inverted) formfor example, at the opposite ends of a transposon.
IR See inverted repeat sequence.
IS See insertion sequence.
isoaccepting tRNAs The various types of tRNA molecules that carry a specific amino acid.
isotope One of several forms of an atom having the same atomic number but differing atomic masses.

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