Q u an t h e t u p h o i la qu an t h e c6 cac ca t h e sin h san h ih i t in h b an g t ir t h u t in h
hoac t ir t h u p h an . C5 qu an t h e t u p h o i, c6 t i le k i^ u gen khong t h eo co n g t h u c cu a djn h luat H a cd i-Va n b e r g (khong can bang di truyen).
- D o i va i qu an t h e t u p h o i, k h i t in h t i le k ie u gen p h ai can c u vao t i le k ie u gen Aa th eo con g t h u c:
The he xuat phat cua rnqt quan the ty phoi c6 xAA + yAa + zaa = 1. Thitfthe he F„: y ti le kieu gen Aa = 2" ti le kieu gen AA = x + y - ti le kieu gen aa = z + — B. CAC DANG BAI TAP THUCING GAP 1. Dang bai toan chi c6 1 cap gen
Doi vol dang bai tap nay thi nen tien hanh theo 3 bu-ffc sau:
Budfc 1: Xac dinh cau true di truyen ciia quan the o* thoi diem tinh xac suat Buffc 2: Tim ti le cua loai kieu hinh (hoac kieu gen) can tinh xac suat Buac 3: Sir dung toan to hgp de tinh xac suat
Bai 1: M o t qu an t h e t u p h o i a t h e he xu at ph at c6 t i le k ie u gen la 0,1 A A : 0,4Aa :
0,5aa. CJ t h e he F2, lay n gau n h ien 1 ca t h e, xac suat de t h u d u gc ca t h e t h u an ch u n g la bao n h ieu ?
Huang dan gidi:
Buac 1: Xac dinh cau tnic di truySn cua quSn thS a thai diSm F2
- Khi cac ca the tu phoi thi
0 4
O the he F2 c6 kieu gen Aa chiem ti le = - ~ =0 , 1 .
KiSu gen A A c6 ti le = 0,1+ M z M = o,25.
Kiku gen aa c6 ti le = 0,5+ = 0,65.
- Cau true di truyen cua quan the a the he F2 la 0,25 AA + 0,1 Aa + 0,65aa =1.
Buac 2: Tim ti le ca thI thuin chung a F 2 .
Ca the thuan chung gom c6 0,25AA va 0,65aa.
-> d F 2 , ca t h e thuSn chung chi6m ti le = 0,25 + 0,65 = 0,9.
Buac 3: Su dung toan to hop de tinh xac suat
Lay ngau nhien 1 ca the thi xac suit dk thu dugc ca thI thuin chung = 0,9.
Bai 2: O mot loai thuc vat, gen A quy dinh hoa do troi hoan toan so voi alen a quy
dinh hoa vang. The he xuat phat cua mot qukn thk tu ph6i c6 t i le kidu gen la 0,2AA : 0,8Aa. C> the he F 3 , lay ngau nhien 3 cay, xac suit dk thu dugc 2 cay hoa do la bao nhieu?
Huang dan gidi:
Buac 1: Xac dinh cau tnic di truyen cua quan the a thai diem F3
- Khi cac ca the tu phoi thi
0 8
O the he F3 c6 kieu gen Aa chiem ti le = =0 , 1 .
K i l u gen A A c6 ti le = 0,2 + MzM = 0 ,55.
KiSu gen aa c6 t i le = 0 + = 0 ,35.
- Cau tnic di truyen cua quan the a the he F3 la 0,5 5 A A + 0,1 Aa + 0,3 5aa =1. (adsbygoogle = window.adsbygoogle || []).push({});
Buac 2: Tim ti le cay hoa do va cay hoa tr^ng a F 3 .
cau true di truySn cua quan th8 a thS he F3 la 0,55AA + 0,1 Aa + 0,35aa =1 -> Cay hoa do (AA va Aa) chiSm ti le = 0,55 + 0,1 = 0,65.
Cay hoa trang (aa) chilm ti le = 0,35.
Buac 3: Sur dung toan t6 hgfp dk tinh xac suit
(3 the he F 3 , lay ngau nhien 3 cay, xac sudt d l thu dugc 2 cay hoa do la
Ba i 3: CJ mot loai thirc vat sinh san bang t u thu phan, gen A quy dinh hoa do troi hoan toan so v a i a quy dinh hoa trang. The he xuat phat cua mot quan thk c6
100% cay hoa do. CJ the he F2, cay hoa trSng chi^m t i le 9%. hiy ngau nhien 2 cay hoa do a Fj, xac suat de thu duoc 1 cay thuan chiing la bao nhieu?
Huang dan giai:
Buac 1: Xac dinh cau true di truyen cua quan the a thai diem F2
- Goi t i le kieu gen a the he xuat phat la (1 -x) A A : x A a
-dthkhe F2 CO t i le cay hoa trSng = 9% = 0,09. O the he F2 , kieu gen A a c6 t i le = - y = —
Kieu gen aa c6 t i le = 0 + 8 X 0,09 X x — 4 3x = 0,09 - >x = 0,24 = 24%.
- Vay cau tnic di truyen a the he xukt phat la 0,76AA + 0,24Aa =1 .
- d the he F2 CO A a = - = = 0,06. 4 4
A A CO t i le = 0,76 + 0,24 - 0,06 = 0,85
aa CO t i le = 0,24 - 0,06 = 0,09.
-> C i u tnic di truyen a thk he F2 la 0,85AA + 0,06Aa + 0,09aa = 1.
BUffc 2: T i m t i le ca the thuan chung trong so cac cay hoa do a F2
CJ F2 CO ciu tnic di truySn la 0,85AA + 0,06Aa + 0,09aa = 1 -> Cay hoa do gom c6 0,85AA va 0,06Aa.
0 85
Trong so cac cay hoa do, cay thuan chung chiem t i le = -0,85 + 0,06 - 0 , 9 3 Cay khong thuan chung chiem t i le = 1 - 0,93 = 0,07.
Buac 3: Su dung toan to hop de tinh xac suit
Lay ngau nhien 2 cay hoa do a F2, xac suat de thu duofc 1 cay thuan chung la C',xO,93xO,07 =0 , 1 3 .
Bai 4: C) mot loai thuc v^t sinh san bang t u thu phdn, gen A quy dinh hoa do troi hoan toan so v a i a quy dinh hoa trang. The he xuat phat cua mot quan the c6 t i le kieu hinh 90% cay hoa do, 10% cay hoa t r i n g . C) t h ^ he F2 , cay hoa t r i n g chiem t i le 40%. N ^u a F2, cac ca t h i giao phAn ngau nhien thu dugrc F3. Lky
Huong dan gidi:
Buac 1: Xac dinh cau true di truyen cua quan the a thai diem F2