GENETICS: H. S. JENNINGS 49 
(20) Inbreeding, brother by sister, when the original cross was AA 
by Aa. After n inbreedings: 
AA = M^. Aa = ?^. aa = 5fLti. 
Bn + 3 Bn4.2 + 3 
(21) Inbreeding, parent by offspring; parents AA by Aa; progeny 
mated back continually to Aa: 
AA = ^^. Aa=i aa = -^. 
(22) Sex-linked characters; a cross between AA and a — , then 
breeding by random mating. After n random matings: 
Males: A - = thus, 1/2, 3/4, 5/8, etc. 
a - = 5?: thus, 1/2, 1/4, 3/8, etc. 
Females: AA = ^"^^" + ^ ; thus 1/2, 3/8, 15/32, 55/128, etc. 
B2n-1 
aa = GnXGn-i. ^j^^g ^^g^ 3^32^ 15/128, etc. 
B2n - 1 
Aa = 1 - AA - aa; thus 1/2, 4/8, 14/32, 58/128, etc. 
Males and females equal in number. 
(23) Sex-linked characters; a cross between AA and a — , then in- 
breeding, brother by sister. After n inbreedings: 
Males: A - = a - = 
Bn B, 
Females: AA =h±l, Aa =1^. aa = 5^^^. 
Bn + l Bn Bn^.! 
(24) Sex-linked characters; cross between AA and a — , then inbreed- 
ing, daughters mated to fathers, sons to mothers (as could be carried 
out only in certain lower Organisms). After n inbreedings: 
Males: A - = ^^n+i. ^^^^^ 3/4^ ^^^^^^ 43/^4^ ^^^^ 
B211 
a - = ^: thus, 1/4, 5/16, 21/64, etc. 
Bon 
