Heredity in ophthalmology / Jules François.

  • François, J. (Jules)
Date:
1961
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Heredity in ophthalmology / Jules François. Source: Wellcome Collection.

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    SEX-LINKED INHERITANCE 35 ò-- C.- liyi?' 4-s-.b Y ь — с — d Fig. 17. Schematic rep¬ resentation of the X and Y sex chromosomes. Parents Gametes 46 + XX ,23+X [23* X Offspring [46+XX Fig. 18. The determination of sex. DOMINANT GENE CARRIED ON THE UNPAIRED SEGMENT OF THE X CHROMOSOME Let us consider the case of a normal man (xY) and a woman (Xx), a hetero¬ zygote for a pathologic dominant gene located on the X chromosome (Fig. 19). The woman produces two kinds of ova—namely, ova with the pathologic gene (X) and normal ova (x). The man produces spermatozoa of two kinds, those with the normal X and those with the Y chromosome. Four combinations become possible at fertilization: (1) an X chromosome with the gene fcr the disease and a normal X chromosome, (2) an X chromosome with the disease and a Y chromosome, (3) two normal x chromosomes, and (4) a normal x chromosome and a Y chromo¬ some. The offspring will be a diseased female (Xx), a diseased male (XY), a Affected woman Normal man Parents Gametes Offspring Affected girl Affected boy Normal girl Normal boy Fig. 19. Dominant sex-linked heredity. Crossing between a heterozygous woman for a dominant gene carried on the X chromosome and a normal man.