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.

    48/750 (page 44)
    44 GENERAL GENETICS I IT ж Ш □ i ¿ I »il & ÔDÛ 1 ¥é uò oiiio¿ii □ ïihi lili □ □ Fig. 33. Dominant incomplete sex-linked heredity. Pigmentary retinopathy. (After Snell, 1903.) Heterozygote woman Heterozygote man Parents Gametes Offspring (X И )< \xà Affected girl Boy carrier Girl carrier Normal boy Fig. 34. Recessive incomplete sex-linked heredity. Crossing of a father and a mother, both carrying the pathologic gene on the paired segment of the X chromosome. his daughters but to none of his sons, whereas a man receiving a trait from his father transmits it to all his sons but to none of his daughters. The offspring of an affected man comprise daughters that resemble their paternal grandmother and sons that resemble their paternal grandfather (Fig. 32). A pedigree of pigmentary retinopathy (Fig. 33) provides an example of a dominant gene incompletely sex linked. All the daughters of a man showing this abnormality also show it, whereas all his sons are normal. Half of the sons and daughters of a woman showing the same disorder also have retinopathy. There are, however, in this pedigree some peculiarities that are explainable by crossing over. III-A has a son who is pathologically affected and two normal daughters. There must have been three instances of crossing over. The son IV-B with retinopathy must be carrying the pathologic gene on his Y chromosome and should transmit it only to sons, but in actual fact one son (out of seven) is