Why the individual 3 in Family G (generation 4) is not considered as recombinant

Question

Why the individual 3 in Family G (generation 4) is not considered as recombinant? Family A Family B FIGURE 15.7 Pedigree of two sox Generation linked recessives, color blindness and G6PD deficiency. Among 3648 black schoolboys, color blinaness was found in 134 (3.7 percent). All males (totaling 236) in the sibships of 106 of the colorblind probands were testea for Ga- In 10 sibsnips, both traits were discovered; six of these families (having the ceutan type of coior blindness) are diagram- mea nere. Only one cefinite instance of recombination was discoverea, in famly H (indicatea by the asterisk in the pedigree cnan) Numbers beiow the sym- bols indicate ages at time of testing: numbers above and to the left ot symbols identify inaividuais within each generation (After VA 37 43 72 20 17 15 22 5 6 12 6 Family D Family E 23 McKusick. On tne X Chromosome of Man. American institute of Bo- togical Sciences. 1962.1 35 29 24 38 36 1 2 10 7 25 24 12 8 Family G Family H 2 65 60 57 52 39 37 26 28 26 23 112. 3 24 11 G 10 8 5 Doubly affected male Color-blind male Unaffected male unaffected female Dead Z Gd male

Explanation / Answer

Case 1:

IV-3 individual is affected by both the disorder, as we observe here noneneof his ancestors had double affected.If his mother had double affected X chromosome,it must be carier. The X chromosome in her mother must be inherited from IV 3's Grand father who is dead.

Case 2:

The individual IV 3 is doubly affected except his dead grand father none of the male ancestors had this affected X chromosome.

Conclusion so he can't be recombinant. Though it is type of Cris cross inherited. From maternal Grand father to mother to son.

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