Megabase pairs
One of the pairs of chemical bases joined by hydrogen bonds that connect the
complementary strands of a DNA molecule or of an RNA molecule that has two strands; the
base pairs are adenine with thymine and guanine with cytosine in DNA and adenine with
uracil and guanine with cytosine in RNA
Megapascal (MPa)
A unit of pressure equivalent to 10 atmospheres of pressure.
Megaspore
In plants, a haploid spore that develops into a female gametophyte.
Meiosis or reduction division
A two-stage type of cell division in sexually reproducing organisms that results in gametes
with half the chromosome number of the original cell.
Melanoma
A tumor arising from the melanocytic system of the skin and other organs.
Melanocyte -stimulating hormone
A hormone secreted by the pituitary gland that regulates skin color in humans and other
vertebrates by stimulating melanin synthesis in melanocytes and melanin granule dispersal
in melanophores. Also called intermedin.
Membrane potential
The charge difference between the cytoplasm and extracellular fluid in all cells, due to the
differential distribution of ions. Membrane potential affects the activity of excitable cells
and the transmembrane movement of all charged substances.
Memory cell
A clone of long-lived lymphocytes, formed during the primary immune response, that
remains in a lymph node until activated by exposure to the same antigen that triggered its
formation. Activated memory cells mount the secondary immune response.
Mendel's first law
The principle, originated by Gregor Mendel, stating that during the production of gametes
the two copies of each hereditary factor segregate so that offspring acquire one factor from
each parent.
ff
(ff)
#1