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multiple endocrine neoplasia.


(mĕn-ăk′tră) Meningococcal vaccine.


quadrivalent meningococcal conjugate vaccine.


(mĕn-ăr′kē) [Gr. men, month, + arche, beginning] The initial menstrual period, normally occurring between the 9th and 17th year. SEE: adrenarche; puberty. menarchal, menarcheal, menarchial, adj.

Mendel, Kurt

(mend′ĕl) Ger. neurologist, 1874–1946.

M.-Bechterew reflex SEE: Mendel-Bechterew reflex.

Mendel-Bechterew reflex

[Mendel, Kurt + Bechterew, Vladimir Mikhailovich] Plantar flexion of the toes in response to percussion of the dorsum of the foot.


(men″dĕ-lē′vē-um) [Dmitri Mendeleyev, Russian chemist, 1834–1907 + -ium (1)] SYMB: Md. A transuranium element; atomic weight (mass) 256, atomic number 101.


(mĕn′dĕl-ĭzm) The principles of heredity expressed in Mendel's laws.

Mendel laws

(men′dĕl) [Gregor Johann Mendel, Austrian monk, 1822–1884] The laws governing the genetic transmission of dominant and recessive traits. By carefully studying the heredity characteristics of garden peas, Mendel was able to explain the transmission of certain traits from one generation to the next.

Many inherited characteristics are controlled by the interaction of two genes, one from each parent. During meiosis, parent cells divide and contribute half their chromosome complement to the egg or sperm. After fertilization, the zygote contains a pair of each chromosome; each pair has genes for the same traits at corresponding locations. Alternate forms of the gene for a specific trait are called alleles, which may be dominant or recessive. SEE: allele; chromosome; gamete; gene; meiosis.

Mendel's law of segregation states that as the gametes are formed, the gene pairs separate and do not influence each other.

Mendel's law of dominance resulted from his observation that crossing a tall strain of peas with a short strain resulted in the expression of the dominant trait, in this case tallness. Thus, a dominant trait will appear in the individual even if only one allele for it is present in the genome.

Mendel's law of independent assortment states that traits controlled by different gene pairs (such as height and color) pass to the offspring independently of each other.

Ménétrier disease

(mā-nā-trē-ā′) [Pierre Ménétrier, Fr. physician, 1859–1935] Giant hypertrophic gastritis.

Ménière disease

(mĕn-yer′) [Prosper Ménière, Fr. physician, 1799–1862] A disorder of the inner ear characterized by recurring episodes of hearing loss, tinnitus, vertigo, and aural fullness, often resulting in gradually progressive deafness. Exacerbations (such as vertigo) may occur suddenly and last for as long as 24 hr. When one ear is affected, ...

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