twins--What Online Mendelian Inheiritance in Man has to say

Eric R. Hugo e_hugo at
Thu Oct 13 07:29:54 EST 1994

Dear Bionetters,
	I took the time to see what the authorities have to say on the subject of 
twins and this is what I dug up: (excerpted from V. McKusick's OMIM)

OMIM -- 276400
Weinberg (1909) suggested that hereditary twinning is transmitted only through the female line,
 applies only to dizygotic twins, and is probably recessive. Observation 
of multiple births following use of pituitary gonadotropins suggests a 
pituitary mechanism for gene action Wyshak and White (1965) presented 
evidence, based on Mormon records, which they interpreted as supporting 
recessive inheritance. Among the children of female DZ twins, 17.1 twins per 
1000 maternities occurred as compared with 7.9 among children of male DZ 
twins. Female sibs of DZ twins had 17 per 1000 twins, whereas male sibs had 
13.1 per 1000. Supposedly the gene is too frequent for one to expect increased 
consanguinity in the grandparents of dizygotic twins. Taylor (1931) 
reported multiple sets of dizygotic twins in 4 generations. In the same 
family, mother and daughter did not menstruate until after their first 
pregnancies, at ages 20 and 22, respectively. The differentiation of 
multifactorial and monofactorial inheritance of twinning is difficult. Ethnic 
differences in the rate of dizygotic twinning is evidence of genetic facrs. In 
interracial marriages the rate follows that of the mother's ethnic oup. 
Furthermore, when the mother is a racial hybrid, the dizygotic twinning 
equency is that of the race with the lower frequency Morton  
al., 1967).

OMIM -- 276410
Although the frequency of monozygotic twinning has been said to be
 uninfluenced by genetic factors,Harvey et al. (1977)
 reported 10 families with multiple pairs of monozygotic twins and sugge
sted that the question should be reexamined. Both fathers and mothers were 
represented among MZ twin parents of MZ twins. Shapiro et al. (1978) reported 
a kindred with 4 sets of monozygotic twins and favored autosomal dominant 
inheritance for a subset of monozygotic twins.  Derom et al. (1987) found a 
significant increase in the frequency of zygotic splitting producing 
monozygotic twins and triplets after artificial induction of ovulation. This 
may be the first identified biological mechanism influencing the monozygotic 
twinning rate.

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Eric Hugo, Ph.D.// |:,\\': | \\      // | :,\\': | \\      // | :,\\': | \\
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Asst. Professor, Biology  \\ | :,\\': | //      \\ | :,\\': | //      \\ |
Dickinson State University  \\ //  \\ //          \\ //  \\ //          \\
Dickinson, ND  58601    |finger eric at for public key

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