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phylogeny:
Evolutionary history of an organism or group of organisms, often
presented in chart form as a phylogenetic tree.
pinocytosis:
Type of endocytosis in which soluble materials are taken up
from the environment and incorporated into vesicles for digestion.
Literally, "cell drinking."
plasma membrane:
Membrane that surrounds a living cell.
plasmid:
Small circular DNA molecule that replicates independently of
the genome. Used extensively as a vector for DNA cloning.
plasmodesma (plural plasmodesmata):
Communicating cell-cell junction in plants in which a channel
of cytoplasm lined by plasma membrane connects two adjacent
cells through a small pore in their cell walls.
plastid:
Cytoplasmic organelle in plants, bounded by a double membrane,
that carries its own DNA and is often pigmented. Chloroplasts
are plastids.
platelet:
Cell fragment, lacking a nucleus, that breaks off from a megakaryocyte
in the bone marrow and is found in large numbers in the bloodstream.
It helps initiate blood clotting when blood vessels are injured.
plus end:
The end of a microtubule or actin filament at which addition
of monomers occurs most readily; the "fast-growing"
end of a microtubule or actin filament. The plus end of an actin
filament is also known as the barbed end.
point mutation:
Change of a single nucleotide in DNA, especially in a region
of DNA coding for protein.
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