biology-dictionary_11-06-2009

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Mesonephric
excretory tube of the mesonephros; becomes the mesonephric duct and contributes in the adult to
the vasa efferentia of the male.
Mesonephric tubules are genital ridges that are next to the mesonephros. The excretory
organ serving as the adult kidney of fishes and amphibians and as the embryonic kidney of
higher vertebrates: the mesonephros and its duct develop into the epididymis and vas
deferens in higher vertebrates
Mesozoic
Belonging to, or designating the era of geologic time that includes the Triassic, Jurassic, and
Cretaceous periods and is characterized by the development of flying reptiles, birds, and
flowering plants and by the appearance and extinction of dinosaurs.
Messenger RNA (mRNA)
A type of RNA synthesized from DNA in the genetic material that attaches to ribosomes in
the cytoplasm and specifies the primary structure of a protein.
Metabolism
The totality of an organism's chemical processes, consisting of catabolic and anabolic
pathways.
Metacarpals
Any bone of the hand between the wrist and fingers
Metacentric
Having the centromere in the median position so that the arms are of equal length. Used of
a chromosome.
Metagenesis
Alternation of sexual and asexual generations.
Metamere
Any of the homologous segments, lying in a longitudinal series, that compose the body of
certain, such as earthworms and lobsters. Also called somite.
Metanephric
One of the three embryonic excretory organs of higher vertebrates, becoming the
permanent and functional kidney.

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