. Preventive medicine and hygiene. nt fromskin, hair, and eyes. Themethod of inheritance re-sembles that of eye both parents lackpigment, all offspring arelikewise devoid of one parent only is analbino and the other is un-related, then the childrenare all pigmented. When-ever pigmented parents havealbino children, the pro-portion of the albinos ap-proaches the ideal and ex-pected Mendelian propor-tions—25 per cent. Daven-port points out that albinosmay avoid albinism in theiroffspring by marrying un-related pigmented persons belong-ing to albinic strai
. Preventive medicine and hygiene. nt fromskin, hair, and eyes. Themethod of inheritance re-sembles that of eye both parents lackpigment, all offspring arelikewise devoid of one parent only is analbino and the other is un-related, then the childrenare all pigmented. When-ever pigmented parents havealbino children, the pro-portion of the albinos ap-proaches the ideal and ex-pected Mendelian propor-tions—25 per cent. Daven-port points out that albinosmay avoid albinism in theiroffspring by marrying un-related pigmented persons belong-ing to albinic strains mustavoid marrying cousins,even pigmented ones, be-cause both parents might,in that case, have albinicgerm cells and produce onechild in four albinic. Al-bino communities, of whichthere are several in theUnited States, are inbred communities, but not all inbred communitiescontain albinos. Color-blindness, or Daltonism.—Color-blindness, or daltonism, is acondition probably not localized in the eyes, but due to some defect in. THE HEEEDITAEY TRANSMISSIOX OF DISEASE 507 the central nervous structure. It is transmitted hereditarily. Color-blindness is much commoner in men than in women. A color-blind man,however, does not transmit color-blindness to his sons; the daughters,also, are themselves normal, provided the mother was, yet the daugh-ters transmit color-blindness to half their sons. A color-blind daughtercould be produced apparently only by the marriage of a color-blind manwith a Avoman who transmits color-blindness, since the daughter, to becolor-blind, must have received this unit character from both parents,whereas the color-blind son receives the character only from his mother;that is, the condition is sex-limited. Color-blindness is apparently due to a defect in the germ cell—absence of something normally associated there, with an X-structurewhich is represented twice in women, once in men. The following interesting family history, studied by Horner, showsthe he
Size: 960px × 2604px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorwh, bookcentury1900, bookdecade1910, booksubjecthygiene
