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Form 20-F

In the USA, the form required by the Securities and Exchange Commission for the filing of annual results by non-US companies.

immunoelectron microscopy

immunoelectron microscopy  

A form of transmission electron microscopy (see electron microscope) in which the specimen is treated with gold-labelled antibodies specific for the protein component of interest. The gold labels are ...
gramicidin S

gramicidin S  

A cyclic antibiotic synthesized by Bacillus brevis. The molecule has the structure [d-phe–pro–val–orn–leu leu–orn–val–pro–d–phe] and it contains amino acids not usually found in proteins—namely, ...
ammonotelic

ammonotelic  

Describing animals that excrete nitrogenous waste in the form of ammonia. Most aquatic animals are ammonotelic. Compare ureotelic; uricotelic.
kinetoplast

kinetoplast  

A highly specialized mitochondrion associated with the kinetosome of trypanosomes. Kinetoplast DNA is the only DNA known in nature that is in the form of a network consisting of interlocked circles. ...
wild type

wild type  

Describing the form of an allele possessed by most members of a population in their natural environment. Wild-type alleles are usually dominant.
Ernst Haeckel

Ernst Haeckel  

(1834–1919)German biologist, who became professor of zoology and comparative anatomy at the University of Jena in 1862. An ardent follower of Darwin, Haeckel was the first to divide animals in ...
conjugation

conjugation  

1 The fusion of two reproductive cells, particularly when these are both the same size (see isogamy).2 A form of sexual reproduction seen in some algae (e.g. Spirogyra), some bacteria (e.g. ...
cladogenesis

cladogenesis  

In cladistics, the derivation of new taxa (see taxon) that occurs through the branching of ancestral lineages, each such split forming 2 equal sister taxa that are taxonomically separate from the ...
hemimetabolous

hemimetabolous  

Applied to those insects in which the adult form is attained by a series of moults, and metamorphosis is incomplete. All the immature stages are called nymphs.
Monera

Monera  

In some taxonomic schemes, one of the 5 kingdoms of life, comprising the prokaryotic Cyanophyta' (cyanobacteria) and ‘Schizomycophyta’ (other bacteria). Prokaryotes are currently placed into more ...
phagocytosis

phagocytosis  

A form of endocytosis in which a cell membrane invaginates and encloses externally derived, solid material within a vacuole, without disrupting the continuity of the cell surface. Subsequently this ...
SOS response

SOS response  

A cellular response to extensive DNA damage in which certain genes, called SOS genes, are sequentially activated in order to repair the damaged DNA. In E. coli about 20 such genes have been ...
red tide

red tide  

A sudden often toxic proliferation of marine phytoplankton, notably dinomastigotes, that colours the sea red, brown, or yellowish due to the high concentration of the organisms' photosynthetic ...
homeobox

homeobox  

In an embryo, a family of genes that cause the embryo to subdivide as it grows, to form groups of cells which will develop into particular organs and tissues.
metamorphosis

metamorphosis  

The transformation from larval to adult form. In Drosophila the destruction of larval tissues and their replacement with adult ones is triggered by 20-hydroxy-ecdysone. See ecdysones.
biochemistry

biochemistry  

The study of the chemistry of living organisms, especially the structure and function of their chemical components (principally proteins, carbohydrates, lipids, and nucleic acids). Biochemistry has ...
haploid

haploid  

Describing a nucleus, cell, or organism with a single set of unpaired chromosomes. The haploid number is designated as n. Reproductive cells, formed as a result of meiosis, are haploid. Fusion of two ...
histone

histone   Reference library

Oxford Dictionary of Biochemistry and Molecular Biology (2 ed.)

Reference type:
Subject Reference
Current Version:
2008
Subject:
Science and technology, Life Sciences
Length:
123 words

...25%, and are concerned in the packing of DNA in chromatin . The principal histones may be classified into five types, as shown in the table. Type Other names Lys/Arg ratio M r Location H1 F1,Ia 20.0 21 000 linker H2A F2a2,IIb1 1.25 14 500 core H2B F2b,IIb2 2.25 13 800 core H3 F3,III 0.72 15 300 core H4 F2a1,IV 0.79 11 300 core The octomer (H2A,H2B,H3,H4) 2 forms the nucleosome core. H1 is associated with nucleosomes, especially the linking DNA. See also H‐NS...

popcorn

popcorn   Quick reference

A Dictionary of Genetics (8 ed.)

Reference type:
Subject Reference
Current Version:
2014
Subject:
Science and technology, Life Sciences
Length:
133 words
Illustration(s):
1

...to heat and form fluffy white puffs. The earliest Zea mays ( q.v. ) to be cultivated was a popcorn that evolved in Mexico at different altitudes and culturing conditions, and it underwent introgressive hybridization ( q.v .) with teosinte ( q.v. ). A popcorn such as the Tom Thumb (short plants with small ears) has a genome size 20% smaller than a sweet corn such as Black Mexican. See kernel . Quantitative inheritance in maize . Distribution of ear lengths in parents, F 1 , and F 2 generations of...

genetic erosion

genetic erosion   Quick reference

A Dictionary of Plant Sciences (4 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Life Sciences
Length:
198 words

...erosion The loss of genetic information that occurs when highly adaptable cultivars are developed and threaten the survival of their more locally adapted ancestors, which form the genetic base of the crop. For example, a new hybrid strain of maize ( Zea mays ), developed largely by Donald F. Jones from a variety discovered in 1917 , had yields 25 per cent greater than standard maize. By the 1960s it was economically very favourable to use this single hybrid type, and more traditional varieties rapidly receded in distribution. The widespread...

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