Dipeptides
A dipeptide is a molecule consisting of two amino acids joind by a single peptide bond.
Diploid cell
A cell containing two sets of chromosomes (2n), one set inherited from each parent.
Diplobalstic
They have two germ layers - or a two - layerd body wall. The epidermis and gastrodermis.
Diplotene
A stage of meiotic prophase in which homologous chromosome pairs begin to separate and
chiasmata become visible.
Directed molecular evolution
A laboratory version of evolution at the molecular level that can produce "designer
molecules." A large starting population of molecules (typically nucleic acids) that varies
randomly in base sequence and shape is subjected to replication with variation, followed by
selection. After several cycles of replication and selection, the population of molecules will
evolve toward one containing a high proportion of molecules well adapted to the selection
criterion applied.
Directional selection
Natural selection that favors individuals on one end of the phenotypic range.
Disaccharide
A double sugar, consisting of two monosaccharides joined by dehydration synthesis.
Diurnal
Applied to organisms that are active during the daylight hours.
Dispersion
The distribution of individuals within geographical population boundaries.
Diversifying selection
Natural selection that favors extreme over intermediate phenotypes.
Division
A taxonomic grouping of related, similar classes; a high- level category below kingdom and
above class. Division is generally used in the classification of prokaryotes, algae, fungi, and
plants, whereas an equivalent category, phylum, is used in the classification of protozoa and
animals.
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