Biology Glossary - U

Uracil (or the corresponding nucleoside or nucleotide) in a nucleic acid.

 see snrna.

U1–U6 snRNAs

 see split gene (a).

Upstream activation site: a sequence in the DNA of Saccharomyces cerevisiae which is involved in the regulation of transcription; it apparently resembles an enhancer except that it cannot function when located downstream of a promoter.

See quinones
A polypeptide (containing 76 amino acids) present – either free or covalently bound to protein – in the cells of higher eukaryotes and in various microorganisms. Energy-dependent binding of ubiquitin to a protein is apparently an essential signal for the selective proteolysis of that protein in the cell. The ubiquitin–PROTEASOME pathway has been reported to be essential for proteolysis during morphological changes in Trypanosoma cruzi 

ultimate causation

The hypothetical evolutionary explanation for the existence of a certain pattern of animal behavior.
unsaturated fatty acid
A fatty acid possessing one or more double bonds between the carbons in the hydrocarbon tail. Such bonding reduces the number of hydrogen atoms attached to the carbon skeleton.
[Gk. ouron, urine]
A soluble form of nitrogenous waste excreted by mammals and most adult amphibians.
[Gk. from ourein, to urinate]
A duct leading from the kidney to the urinary bladder.
[Gk. from ourein, to urinate]
A tube that releases urine from the body near the vagina in females or through the penis in males; also serves in males as the exit tube for the reproductive system.
uric acid
[Gk. ouron, urine]
An insoluble precipitate of nitrogenous waste excreted by land snails, insects, birds, and some reptiles.
[Gk. ouron, urine]
The liquid waste filtered from the blood by the kidney and stored in the bladder pending elimination through the urethra.
A chordate without a backbone, commonly called a tunicate, a sessile marine animal.
[L. womb]
A female reproductive organ where eggs are fertilized and/or development of the young occurs.

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