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Incidence of 47,XYY males:Implications of the production of47,XYY offspring by 47,XYY malesElizabeth Dorus a & John Gillespie ba Department of Psychiatry , University of Chicago , 950 East59th Street, Chicago, Illinois, 60637b Department of Biology , University of Pennsylvania ,Philadelphia, PennsylvaniaPublished online: 23 Aug 2010.

To cite this article: Elizabeth Dorus & John Gillespie (1978) Incidence of 47,XYY males:Implications of the production of 47,XYY offspring by 47,XYY males, Biodemography and SocialBiology, 25:2, 87-93, DOI: 10.1080/19485565.1978.9988326

To link to this article: http://dx.doi.org/10.1080/19485565.1978.9988326

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Incidence of 47,XYY Males: Implications ofthe Production of 47,XYY Offspring by47,XYY Males

Elizabeth Dorus and John Gillespie

Department of Psychiatry, University of Chicago, Chicago, Illinois; and Department of Biology, University ofPennsylvania, Philadelphia, Pennsylvania

ABSTRACT: Chromosomally normal 46,XY males can have 47,XYY male offspring as a result offertilization of a normal ovum by a YY spermatozoon, produced by nondisjunction in the secondmeiotic division or by mitotic nondisjunction of the Y chromosome in early stages of embryonicdevelopment of a 46,XY fetus. If such meiotic and mitotic nondisjunctions were random events andif these were the only source of 47,XYY males in the population, the incidence of 47,XYY maleswould remain constant. Two cases have been reported, however, in which 47,XYY males pro-duced 47,XYY male offspring. If there are 47,XYY males who are a source of 47,XYY males in thepopulation, there is the possibility that the incidence of 47,XYY males is changing. A discrete-generation model is presented which describes (1) the change in incidence of 47,XYY males fromone generation to the next; (2) the incidence at equilibrium; and (3) the incidence as a function of theprobability that a 47.XYY male has a 47,XYY offspring, and as a function of the mean number ofoffspring of 47,XYY males relative to the mean number of offspring of 46,XY males.

In considering the incidence of the47,XYY male in the population, one gen-erally assumes that the fathers of 47,XYYmales are 46.XY males. Such 47,XYYmales may result from fertilization of anormal ovum by a YY spermatozoon pro-duced in gametogenesis by nondisjunctionin the second meiotic division or may beproduced by mitotic nondisjunction of theY chromosome in early stages of embryonaldevelopment. If there were no systematicvariation in the frequency of occurrence ofthe mechanisms by which 46,XY malesproduce 47,XYY male offspring, and if all47,XYY males were the offspring of46,XY males, the incidence of the 47.XYYkaryotype would remain constant.

In contrast to cases of other sex chromo-some variants in which sterility is the rule(e.g., 45,X and 47,XXY), instances have

Reprint requests should be sent to Dr. ElizabethDorus, Department of Psychiatry, University ofChicago, 950 East 59th Street, Chicago, Illinois60637.

been documented in which 47,XYY maleshave produced chromosomally normaloffspring (e.g., Thompson etal., 1967) and47,XYY males (Tzoneva-Maneva et al.,19661; Sundequist and Hellstrom, 19692).Viable YY spermatozoa could be producedin the 47,XYY male by primary nondis-junction in the second meiotic division as inthe 46,XY male or by secondary nondis-junction. These cases of 47,XYY father-son pairs provide evidence of a secondsource of 47,XYY males in the populationand raise the possibility that the incidenceof 47,XYY males is changing.

We now present a discrete-generationmodel which assumes that 46,XY malesand 47,XYY males can produce 47,XYYmale offspring and which describes (1) thechange in the incidence of 47,XYY males

1 The father and son were 46,XY/47,XYYmosaics, with the latter cell line predominating.

2 The putative father of an illegitimate 47,XYYmale had a 47,XYY karyotype. The Y/E ratios ofboth males, as well as blood typing, provided evi-dence of paternity.

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88 Dorus and Gillespie Social Biology

from one generation to the next; (2) theincidence at equilibrium; and (3) the inci-dence as a function of the probability that a47,XYY male has a 47,XYY offspring,and as a function of the mean number ofoffspring of 47,XYY males relative to themean number of offspring of 46,XY males.Since the model demonstrates the relation-ship between the incidence of 47,XYYmales and reproductive characteristics of46,XY males in comparison to reproduc-tive characteristics of 47,XYY males, itdelineates the kinds of data which would berequired for a better understanding of thepopulation aspects of the 47,XYYkaryotype.

THE MODEL

We propose a discrete-generation modelusing standard modeling techniques. Theassumption of nonoverlapping generationsis commonly made in population genetics;it yields results which can be generalized tooverlapping generations, but with a loss ofclarity. The model describes: Ap, thechange in the incidence of 47,XYY fromone generation to the next;/), the incidenceof 47,XYY males in the population atequilibrium; and y, the incidence of theproduction of 47,XYY males by 46,XYmales. These parameters are defined asfunctions of r, the probability of a 47,XYYmale having a 47,XYY offspring, and ofNJN2, the ratio of the mean total numberof offspring of 47,XYY males reaching re-productive age to the mean total number ofoffspring of 46,XY males reaching repro-ductive age.

TABLE 1

DEFINITION OF MEAN NUMBER OF MALEOFFSPRING PER MALE WHO REACH

REPRODUCTIVE AGE

FATHER

47 XYY46 XY

47.XYY

an

#21

OFFSPRING

46.XY

a12

O22

Let the mean number of male offspringper male who reach reproductive age bedefined as shown in Table 1.

Ifp is the prevalence of 47,XYY males inthe population of fathers and/)' is the prev-alence in the population of offspring, then

, /'flu + qa2ip(an + al2) + q(a2l + a22)

where q = 1 — p.The change in the prevalence of 47,XYY

males from one generation to the next, Ap,is />' —p. If one assumes that an equilib-rium has been reached, i.e., that the preva-lence in the population is not changingfrom one generation to the next, thesteady-state prevalence p is

<• _ pan + qa21

Han q(a21 + a22)

If one expands the denominator of this ex-pression as a geometric series, the termsp2,p3, etc., approximate 0 since p is very small(see Estimation of p below). This expres-sion may then be approximated by

L __ p~(an - a2i)

a22

This statement is equivalent, when theterms are transposed, to

7p =1 - flu — a2\

No

where y is the fraction of male offspring of46,XY males that are 47,XYY, i.e.,

y=__£il__

andiV2 = a21 + a22 is the mean total numberof male offspring of 46,XY fathers. An ad-ditional approximation can be made if onemakes the reasonable assumption that a21/(au + Oi2) is negligible, i.e., that the meannumber of 47,XYY offspring of 46,XYfathers is substantially less than the meantotal number of offspring of 47,XYYfathers. The approximation is

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Vol. 25, No. 2 Incidence of 47,XYY Males 89

1 - r N2

where iVx = an + a12, the mean totalnumber of male offspring of 47,XYYfathers, andr = an/(an + o12), the fractionof male offspring of 47,XYY males that are47,XYY.

lip is known for a particular population,y may thus be estimated by the relationship

provided estimates for r and NJN2 areavailable. The estimation of p, the prob-able limits of r andiVj/iV2, and the charac-teristics of p as r and NJN2 vary are pre-sented below.

ESTIMATION OF f>

The incidence of 47,XYY males is ap-proximated by the prevalence of 47,XYYmales in randomly selected or consecutivenewborn males. Thirty-five 47,XYY maleshave been detected in six samples of new-born males totaling 37,634, resulting in aprevalence of 0.0009, or approximately 1in 1,000 (Hook and Hamerton, 1977). Ifone assumes that differences in prevalenceamong the studies from different geo-graphic areas reflect random rather than re-gional variation, the estimation of the inci-dence is based on a large sample size andshould therefore be reasonably accurate.

ESTIMATION OF r

If the supernumerary Y chromosome of47,XYY males segregated randomly andgametes were equally viable, the value of rcould be determined on the basis of proba-bility. The four types of expected gametesand the probability associated with eachtype would be: X (1/6), Y (1/3), XY (1/3),and YY (1/6). Accordingly, 1/6, or approx-imately 17 per cent, of the offspring couldbe expected to be 47,XYY males. Also,47,XYY males would be expected to pro-duce 47,XXY offspring and twice as many

chromosomally normal males as females.The research done on the presence of thesupernumerary Y chromosome duringgametogenesis in 47,XYY males has beenreviewed by Hulten and Lindsten (1973).Several 47,XYY males studied had onlynormal XY bivalents. However, YY biva-lents have been noted in the cells of two47,XYY males and identified by fluores-cence in one case. This finding confirmsthat, at least in some 47,XYY males, asupernumerary Y chromosome can beperpetuated throughout rather than beingeliminated from the process of gametogen-esis.

One method of estimating r is to deter-mine what per cent of spermatozoa of47,XYY males are YY-bearing. Diasioand Glass (1970) found S per cent YY-bearing spermatozoa in 1,000 ejaculatespermatozoa of a 47,XYY male. In thissubject, 70 per cent of the 1,000 sper-matozoa contained one Y chromosome (orXY) in comparison to 36 to 49 per cent inspermatozoa of normal controls. Faedetal.(1976) found 1.6 per cent YY-bearingspermatozoa in 250 ejaculate spermatozoaof a 47,XYY male in contrast to 0.8 percent of a normal control; Chandley et al.(1976) found 2.4 per cent in 1,600 sper-matozoa of a 47,XYY male, and Hultenand Pearson (1971) found 2.9 per centYY-bearing testicular spermatozoa.

In contrast to the studies of 47,XYYmales, Diasio and Glass (1970) found noYY-bearing spermatozoa in spermatozoaof an unspecified number of 46,XY males;Sumner et al. (1971) found an average of1.3 per cent of YY-bearing spermatozoa in4,000 ejaculate spermatozoa of four sub-jects, three of whom were attending a sub-fertility clinic; and Pawlowitzki and Pear-son (1972) found an average of 1.3 per centin 10,692 ejaculate spermatozoa of twelvehealthy fertile subjects. These studiessuggest that the percentage of YY-bearingspermatozoa may be higher in 47,XYY

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90 Doras and Gillespie Social Biology

males than in 46,XY males, but substan-tially lower than the 17 per cent expected ifthe Y chromosome segregated randomly.Thus, there is no evidence that the addi-tional Y chromosome segregates randomly,but there is evidence that it is not alwayscompletely eliminated in the process ofgametogenesis.

Questions have been raised on opticalgrounds about the validity of inferring thepresence of two Y chromosomes inquinacrine-stained spermatozoa display-ing two fluorescent spots or F-bodies(Roberts and Goodall, 1976). The opticalattenuation coefficient is sufficiently greatthat Y chromosomes located deep in thehead of spermatozoa would not be detectedand other chromosomes and artifactsfluorescing less brightly than the Y locatednear the surface would be detected. In-terobserver variability in the intensity ofthe fluorescence required for a spot to becounted would have a significant effect onthe threshold at which other chromosomeswould become visible and on the resultingcounts of F-bodies. Initially, DNA mea-surements using Feulgen microden-sitometry suggested that the two F-bodiesrepresent two Y chromosomes (Sumner etal., 1971). More recently, DNA measure-ments using integrating microinter-ferometry indicate that DNA measure-ments of spermatozoa with two F-bodiesdo not differ from those of spermatozoawith one F-body, suggesting that many arenot YY-bearing (Sumner and Robinson,1976). The incidence of 47,XYY males, 1in 1,000, is lower than the percentages ofYY-spermatozoa reported in 46,XYmales. YY-bearing spermatozoa may notbe as viable as normal spermatozoa and/orthe percentages reported may representsubstantial overestimations due to techni-cal problems in identifying YY-bearingspermatozoa. In either case, it is likely thatthe percentages of YY-bearing sper-matozoa reported for 47,XYY males willbe overestimations of r.

ESTIMATION OF NJN2

An estimate of NjNt, the ratio of meantotal number of offspring of 47 ,XYY malesto mean total number of offspring of 46 ,X Ymales, depends upon estimating the viabil-ity and reproductivity of 47,XYY males incomparison to 46,XY males. This ratio isdetermined by factors such as (1) viabilityof the 47,XYY fetus, (2) 47,XYY infantmortality, (3) fertility of the 47,XYY male,and (4) the reproductive characteristics of47,XYY males.

To date, no 47,XYY male has been iden-tified in chromosome studies of spontane-ously aborted fetuses (Boue et al., 1976),suggesting that this chromosomal variantdoes not result in a reduced fetal viability.Longitudinal studies of 47,XYY males de-tected in surveys of newborns were begunin the 1960's, and no cases of 47.XYY in-fant mortality have been noted. Jacobs etal. (1974) reported that nine of the ten47.XYY males detected in their investiga-tion were phenotypically normal at birth,and that the tenth had a minor abnormal-ity, namely, bilateral clinodactyly. In asurvey by Lubs and Ruddle (1970), two ofthree 47,XYY males detected had minorneonatal complications. Atone year of age,none evidenced developmental retarda-tion; and at two years, all were doing well.Valentine et al. (1971) have reported thatnone of the four 47,XYY males detected intheir survey showed physical abnor-malities. At four years of age, three werenormal, and one had borderline intelli-gence and behavioral problems. Thesefindings on randomly selected 47,XYYmales constitute the only direct data on theviability of 47,XYY male infants andsuggest a probability that a 47,XYY malewill reach the age of reproduction which isroughly equivalent to the probability for46.XY males.

Gametogenesis has been studied in four47.XYY males detected in a survey of ageneral population (Skakkebaek, 1973), all

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Vol. 25, No. 2 Incidence of 47,XYY Males 91

of whom were found to have impairedspermatogenesis. Three of the four had re-duced sperm counts resulting from the pres-ence of tubules with spermatogenic arrestas manifested in testicular-biopsy speci-mens. The fourth 47,XYY male hadtubules with complete spermatogenesis,but with a reduced number of spermatids.Although one of the 47,XYY males had ason, these data on 47.XYY males whowere not detected in an institutionalized orfertility clinic population strongly suggestthat the fertility of 47,XYY males may onthe average be lower than that of 46,XYmales.

To our knowledge, no data have beenpublished on the mean number of offspringof 47,XYY males in comparison to that of46,XY control males. It may be significantthat the prevalence of 47,XYY males inmental-penal institutions is elevated. Thenature of the relationship between the ele-vated prevalence and the supernumerarychromosome is unclear (Hook, 1973);nevertheless, the possibility exists that47.XYY males have a reduced mean

number of offspring as a function of incar-ceration and subsequent lack of opportunityto reproduce.

In summary, there have been no directstudies of the viability or reproductivity ofthe 47,XYY male which would indicatethat Nt/N2 differs from 1. The data ongametogenesis in 47,XYY males stronglysuggest that NJN2 may be less than 1.However, since this parameter has notbeen systematically investigated, a range ofvalues of NJN2 will be assumed in the dis-cussion of the relationship o{N1/N2 top and7-

CHARACTERISTICS OF f> AND y AS YAND NJN2 VARY

Figure 1 shows the variation in p for arange of values ofr from 0.001 to 0.5, withthe assumption that NJN2 = 1 and y —0.0009. The values of 0.0S and 0.17marked on the abscissa are those, respec-tively, where the percentage of YY-bearingspermatozoa reported for a 47.XYY maleis maximum (Diasio and Glass, 1970), andwhere 17 per cent of the offspring of

18 x 10'.-4.

16 x 10,-4

14 x 10,-4

AP 12 x 10,-4

10 x 10"

8x 10,-4

N/Nj-0.5

• 1

0.001 0.01 0.05 O.I 0.17 0.5

FIG. 1.—Relationship between p and r for iV,/iV2 = 0.5 and 1.0 and y — 0.0009.

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92 Doras and Gillespie Social Biology

10 x 10

8x10

6x10

0 0.2 0.4 0.6 0.8 10 1.2 1.4 1.6 1.8 2.0N,/Nt

FIG. 2.—Relationship between y and Nt/N2 for r = 0.00, 0.03, 0.0S, and 0.17 and^ = 0.0009.

47,XYY males are 47.XYY if randomsegregation and equal viability of gametesare assumed. If one assumes that YY ga-metes have no advantage in regard tosegregation or viability, then 0.17 marksthe upper theoretical limit of r. The lowerlimit is more difficult to specify withoutsystematic research on gametogenesis in47,XYY males and chromosome studies ofoffspring of 47,XYY males. It is evident,however, that, for r equal to or less than0.17, variations in r have very little effecton£. WheniVi/iV2 is less than 1 (e.g., 0.5),as may be the case if 47,XYY males havereduced fertility, the effect on^ is even less,as is also shown in the figure. A theoreticalimplication is that if 47,XYY fetuses of47,XYY fathers were systematicallyaborted, there would be no appreciablechange in the incidence of thischromosomal variant in the population.

Figure 2 shows the values ofy for a rangeof NtIN2 values from 0.0 to 2.0, for f> =0.0009 andr = 0.00, 0.03, 0.05, and 0.17.For r = 0.00 to 0.0S, y does not changeappreciably as NJN2 varies. Also, for thesevalues of r and for somewhat larger values,y — p. Thus, an intervention that wouldeither increase or decrease the mean totalnumber of offspring of 47,XYY males rela-

tive to the mean total number of offspringof 46,XY males would not appreciablyalter the relationship betweeny and^. Forexample, if one assumes that the lowerlimits of r and NJN2 are 0.03 and 0.5,respectively, and that the upper limits are0.05 and 1.5, respectively, then 0.00063 =£y ^ O.OOO77. This example demonstratesthat, if one had accurate estimates of r andNiINi) J could in turn be estimated. Theresulting value of y would predict theproportion of 47,XYY males who could beexpected to have 46,XY fathers and theproportion of those who could be expectedto have 47,XYY fathers.

DISCUSSION

Whereas extensive research has beenaddressed to determining the incidence of47,XYY males in the population, little at-tention has been given to the factors whichcontribute to variations in the incidence.We have focused here on the evidence thatthere may be two types of 4 7 ,X Y Y males inthe population, namely, those who areoffspring of 46,XY males and those whoare offspring of 47,XYY males. In theproposed discrete-generation model, wehave described variation in the incidence of47,XYY males as a function of r, the frac-

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Vol. 25, No. 2 Incidence of 47,XYY Males 93

tion of the total offspring of a 47 ,XYY malewhich is 47,XYY, and NJN2, the ratio ofthe mean total number of offspring of47,XYY males to the mean total number ofoffspring of 46,XY males. The generalconclusion which can be drawn is that,within the probable ranges of r and AyiV2,any reduction in r or NJN2 has no appreci-able effect on the incidence of 47,XYYmales in the population. Thus, the free re-production of 47,XYY males has no ap-preciable effect on the incidence in thepopulation.

The proposed model draws attention tothe fact that little is known about the re-productive characteristics of 47,XYYmales. Assumptions have been made aboutthe ranges within which r and NJN2 arelikely to fall, but it is possible to study theseparameters empirically. One could ascer-tain the mean fraction of offspring of47.XYY males who are 47,XYY males,

that is, the probability that a 47 ,XYY malewill have offspring of the same karyotype.One could also ascertain what the meannumber of offspring of 47,XYY males iscompared to 46,XY normal controls. Lesscentral to the proposed model, but of equalinterest, is the question whether 47,XYYmales have more normal male than femaleoffspring, and whether 47,XYY maleshave 47,XXY offspring. Also, the natureand degree of impairment of viability andfunction of YY-bearing spermatozoa rela-tive to normal spermatozoa needs to beexamined.

ACKNOWLEDGMENTS

This work was supported by the Founda-tions' Fund for Research in Psychiatry and byResearch Scientist Development Award S-K01MH-0011I from the National Institute ofMental Health (Dr. Dorus). Drs. A. P.Amarose, J. D. Rowley, and M. A. Telfer as-sisted in the preparation of the manuscript. E.Lanzl provided editorial assistance.

REFERENCESBOUE, J., M.-J. DAKETSÉ, C. DELUCHAT, N.

RAVISÉ, F. YVERT, and A. BOUÉ. 1976. Identifica-tion par les bandes Q et G des anomalieschromosomiques dans les avortements spontanés.Ann. Génét. 19:233-239.

CHANDLEY, A. C , J. FLETCHER, and J. ROBINSON.1976. Normal meiosis in two 47,XYY men. Hum.Genet. 33:231-240.

DIASIO, R. B., and R. H. GLASS. 1970. The Ychromosome in sperm of an XYY male. Lancet2:1318-1319.

FAED, M., J. ROBERTSON, W. G. MACINTOSH, and J.GRIEVE. 1976. Spermatogenesis in an infertileXYY man. Hum. Genet. 33:341-347.

HOOK, E. B. 1973. Behavioral implications of thehuman XYY genotype. Science 179:139-150.

HOOK, E. B., and J. L. HAMERTON. 1977. The fre-quency of chromosome abnormalities detected inconsecutive newborn studies—Differences betweenstudies—Results by sex and severity of phenotypicinvolvement, p. 63-79. In E. B. Hook and I. H.Porter (eds.), Population cytogenetics: Studies inhumans. Academic Press, Inc., New York.

HULTEN, M., and J. LINDSTEN. 1973. Cytogeneticaspects of human male meiosis. Adv. Hum. Genet.4:327-387.

HULTEN, M., and P. L. PEARSON. 1971. Fluorescentevidence of spermatocytes with two Y chromo-somes in an XYY male. Ann. Hum. Genet.34:273-276.

JACOBS, P. A., M. MELVILLE, S. RATCLIFFE, A. J.KEAY, and J. SYME. 1974. A cytogenetic survey of11,680 newborn infants. Ann. Hum. Genet.37:359-376.

LUBS, H. A., and F. H. RUDDLE. 1970.Chromosomal abnormalities in the human popula-tion: Estimation of rates based on New Havennewborn study. Science 169:495-497.

PAWLOWITZKI, I. H., and P. L. PEARSON. 1972.Chromosomal aneuploidy in human spermatozoa.Humangenetik 16:119-122.

ROBERTS, A. M., and H. GOODALL. 1976. Y chromo-some visibility in quinacrine-stained human sper-matozoa. Nature 262:493-494.

SKAKKEBAEK, N. E., E. ZEUTHEN, J. NIELSEN, andH. YDE. 1973. Abnormal spermatogenesis in XYYmales: A report on 4 cases ascertained through apopulation study. Fertil. Steril. 24:390-395.

SUMNER, A. T., and J. A. ROBINSON. 1976. A differ-ence in dry mass between the heads of X- andY-bearing human spermatozoa. J. Reprod. Fert.48:9-15.

SUMNER, A. T., J. A. ROBINSON, and H. J. EVANS.1971. Distinguishing between X, Y and YY-bearing human spermatozoa by fluorescence andDNA content. Nature (New Biol.) 229:231-233.

SUNDEQUIST, U., and E. HELLSTRÖM. 1969. Trans-mission of 47,XYY karyotype? Lancet 2:1367.

THOMPSON, H., J. MELNYK and F. HECHT. 1967.Reproduction and meiosis in XYY. Lancet 2:831.

TZONEVA-MANEVA, M. T., E. BOSAJIEVA, and B.PETROV. 1966. Chromosomal abnormalities inidiopathic osteoarthropathy. Lancet 1:1000-1002.

VALENTINE, G. H., M. A. MCCLELLAND, and F. R.SERGOVICH. 1971. The growth and development offour XYY infants. Pediatrics 48:583-594.

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